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at89c55 4-169 pdip features ? compatible with mcs-51? products ? 20k bytes of in-system reprogrammable flash memory C endurance: 1,000 write/erase cycles ? fully static operation: 0 hz to 33 mhz ? three-level program memory lock ? 256 x 8-bit internal ram ? 32 programmable i/o lines ? three 16-bit timer/counters ? eight interrupt sources ? low power idle and power down modes description the at89c55 is a low-power, high-performance cmos 8-bit microcomputer with 20k bytes of flash programmable and erasable read only memory. the device is manu- factured using atmels high density nonvolatile memory technology and is compatible with the industry standard 80c51 instruction set and pinout. the on-chip flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. by combining a versatile 8-bit cpu with flash on a monolithic chip, the atmel at89c55 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. 0580d-aC12/97 8-bit microcontroller with 20k bytes flash at89c55 pin configurations pqfp/tqfp plcc (continued)
at89c55 4-170 block diagram port 2 drivers port 2 latch p2.0 - p2.7 flash port 0 latch ram program address register buffer pc incrementer program counter dptr ram addr. register instruction register b register interrupt, serial port, and timer blocks stack pointer acc tmp2 tmp1 alu psw timing and control port 3 latch port 3 drivers p3.0 - p3.7 port 1 latch port 1 drivers p1.0 - p1.7 osc gnd v cc psen ale/prog ea / v pp rst port 0 drivers p0.0 - p0.7
at89c55 4-171 the at89c55 provides the following standard features: 20k bytes of flash, 256-bytes of ram, 32 i/o lines, three 16-bit timer/counters, a six-vector two-level interrupt archi- tecture, a full duplex serial port, on-chip oscillator, and clock circuitry. in addition, the at89c55 is designed with static logic for operation down to zero frequency and sup- ports two software selectable power saving modes. the idle mode stops the cpu while allowing the ram, timer/counters, serial port, and interrupt system to continue functioning. the power down mode saves the ram con- tents but freezes the oscillator, disabling all other chip func- tions until the next hardware reset. the low-voltage option saves power and operates with a 2.7-volt power supply. pin description v cc supply voltage. gnd ground. port 0 port 0 is an 8-bit open drain bidirectional i/o port. as an output port, each pin can sink eight ttl inputs. when 1s are written to port 0 pins, the pins can be used as high- impedance inputs. port 0 can also be configured to be the multiplexed low- order address/data bus during accesses to external pro- gram and data memory. in this mode, p0 has internal pul- lups. port 0 also receives the code bytes during flash program- ming and outputs the code bytes during program verifica- tion. external pullups are required during program verifica- tion. port 1 port 1 is an 8-bit bidirectional i/o port with internal pullups. the port 1 output buffers can sink/source four ttl inputs. when 1s are written to port 1 pins, they are pulled high by the internal pullups and can be used as inputs. as inputs, port 1 pins that are externally being pulled low will source current (i il ) because of the internal pullups. in addition, p1.0 and p1.1 can be configured to be the timer/counter 2 external count input (p1.0/t2) and the timer/counter 2 trigger input (p1.1/t2ex), respectively, as shown in the following table. port 1 also receives the low-order address bytes during flash programming and verification. port 2 port 2 is an 8-bit bidirectional i/o port with internal pullups. the port 2 output buffers can sink/source four ttl inputs. when 1s are written to port 2 pins, they are pulled high by the internal pullups and can be used as inputs. as inputs, port 2 pins that are externally being pulled low will source current (i il ) because of the internal pullups. port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (movx @ dptr). in this application, port 2 uses strong internal pul- lups when emitting 1s. during accesses to external data memory that use 8-bit addresses (movx @ ri), port 2 emits the contents of the p2 special function register. port 2 also receives the high-order address bits and some control signals during flash programming and verification. port 3 port 3 is an 8-bit bidirectional i/o port with internal pullups. the port 3 output buffers can sink/source four ttl inputs. when 1s are written to port 3 pins, they are pulled high by the internal pullups and can be used as inputs. as inputs, port 3 pins that are externally being pulled low will source current (i il ) because of the pullups. port 3 also serves the functions of various special features of the at89c55, as shown in the following table. port 3 also receives the highest-order address bit and some control signals for flash programming and verifica- tion. rst reset input. a high on this pin for two machine cycles while the oscillator is running resets the device. port pin alternate functions p1.0 t2 (external count input to timer/counter 2), clock-out p1.1 t2ex (timer/counter 2 capture/reload trigger and direction control) port pin alternate functions p3.0 rxd (serial input port) p3.1 txd (serial output port) p3.2 int0 (external interrupt 0) p3.3 int1 (external interrupt 1) p3.4 t0 (timer 0 external input) p3.5 t1 (timer 1 external input) p3.6 wr (external data memory write strobe) p3.7 rd (external data memory read strobe)
at89c55 4-172 ale/prog address latch enable is an output pulse for latching the low byte of the address during accesses to external mem- ory. this pin is also the program pulse input (prog ) dur- ing flash programming. in normal operation, ale is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. note, however, that one ale pulse is skipped during each access to external data mem- ory. if desired, ale operation can be disabled by setting bit 0 of sfr location 8eh. with the bit set, ale is active only dur- ing a movx or movc instruction. otherwise, the pin is weakly pulled high. setting the ale-disable bit has no effect if the microcontroller is in external execution mode. psen program store enable is the read strobe to external pro- gram memory. when the at89c55 is executing code from external pro- gram memory, psen is activated twice each machine cycle, except that two psen activations are skipped during each access to external data memory. ea /v pp external access enable. ea must be strapped to gnd in order to enable the device to fetch code from external pro- gram memory locations starting at 0000h up to ffffh. note, however, that if lock bit 1 is programmed, ea will be internally latched on reset. ea should be strapped to v cc for internal program execu- tions. this pin also receives the 12-volt programming enable volt- age (v pp ) during 12-volt flash programming. xtal1 input to the inverting oscillator amplifier and input to the internal clock operating circuit. xtal2 output from the inverting oscillator amplifier. special function registers a map of the on-chip memory area called the special function register (sfr) space is shown in table 1. note that not all of the addresses are occupied, and unoc- cupied addresses may not be implemented on the chip. read accesses to these addresses will in general return random data, and write accesses will have an indetermi- nate effect. user software should not write 1s to these unlisted loca- tions, since they may be used in future products to invoke new features. in that case, the reset or inactive values of the new bits will always be 0. timer 2 registers control and status bits are contained in registers t2con (shown in table 2) and t2mod (shown in table 4) for timer 2. the register pair (rcap2h, rcap2l) are the capture/reload registers for timer 2 in 16 bit capture mode or 16-bit auto-reload mode. interrupt registers the individual interrupt enable bits are in the ie register. two priorities can be set for each of the six interrupt sources in the ip register. data memory the at89c55 implements 256-bytes of on-chip ram. the upper 128-bytes occupy a parallel address space to the special function registers. that means the upper 128- bytes have the same addresses as the sfr space but are physically separate from sfr space. when an instruction accesses an internal location above address 7fh, the address mode used in the instruction specifies whether the cpu accesses the upper 128-bytes of ram or the sfr space. instructions that use direct addressing access sfr space. for example, the following direct addressing instruction accesses the sfr at location 0a0h (which is p2). mov 0a0h, #data instructions that use indirect addressing access the upper 128-bytes of ram. for example, the following indirect addressing instruction, where r0 contains 0a0h, accesses the data byte at address 0a0h, rather than p2 (whose address is 0a0h). mov @r0, #data note that stack operations are examples of indirect addressing, so the upper 128-bytes of data ram are avail- able as stack space.
at89c55 4-173 table 1. at89c55 sfr map and reset values 0f8h 0ffh 0f0h b 00000000 0f7h 0e8h 0efh 0e0h acc 00000000 0e7h 0d8h 0dfh 0d0h psw 00000000 0d7h 0c8h t2con 00000000 t2mod xxxxxx00 rcap2l 00000000 rcap2h 00000000 tl2 00000000 th2 00000000 0cfh 0c0h 0c7h 0b8h ip xx000000 0bfh 0b0h p3 11111111 0b7h 0a8h ie 0x000000 0afh 0a0h p2 11111111 0a7h 98h scon 00000000 sbuf xxxxxxxx 9fh 90h p1 11111111 97h 88h tcon 00000000 tmod 00000000 tl0 00000000 tl1 00000000 th0 00000000 th1 00000000 8fh 80h p0 11111111 sp 00000111 dpl 00000000 dph 00000000 pcon 0xxx0000 87h
at89c55 4-174 table 2. t2contimer/counter 2 control register t2con address = 0c8h reset value = 0000 0000b bit addressable tf2 exf2 rclk tclk exen2 tr2 c/t2 cp/rl2 bit 7 6543210 symbol function tf2 timer 2 overflow flag set by a timer 2 overflow and must be cleared by software. tf2 will not be set when either rclk = 1 or tclk = 1. exf2 timer 2 external flag set when either a capture or reload is caused by a negative transition on t2ex and exen2 = 1. when timer 2 interrupt is enabled, exf2 = 1 will cause the cpu to vector to the timer 2 interrupt routine. exf2 must be cleared by software. exf2 does not cause an interrupt in up/down counter mode (dcen = 1). rclk receive clock enable. when set, causes the serial port to use timer 2 overflow pulses for its receive clock in serial port modes 1 and 3. rclk = 0 causes timer 1 overflow to be used for the receive clock. tclk transmit clock enable. when set, causes the serial port to use timer 2 overflow pulses for its transmit clock in serial port modes 1 and 3. tclk = 0 causes timer 1 overflows to be used for the transmit clock. exen2 timer 2 external enable. when set, allows a capture or reload to occur as a result of a negative transition on t2ex if timer 2 is not being used to clock the serial port. exen2 = 0 causes timer 2 to ignore events at t2ex. tr2 start/stop control for timer 2. tr2 = 1 starts the timer. c/t2 timer or counter select for timer 2. c/t2 = 0 for timer function. c/t2 = 1 for external event counter (falling edge triggered). cp/rl2 capture/reload select. cp/rl2 = 1 causes captures to occur on negative transitions at t2ex if exen2 = 1. cp/rl2 = 0 causes automatic reloads to occur when timer 2 overflows or negative transitions occur at t2ex when exen2 = 1. when either rclk or tclk = 1, this bit is ignored and the timer is forced to auto-reload on timer 2 overflow.
at89c55 4-175 timer 0 and 1 timer 0 and timer 1 in the at89c55 operate the same way as timer) and timer 1 in the at89c51 and at89c52. for further information, see the microcontroller data book, sec- tion titled, timer/counters. timer 2 timer 2 is a 16 bit timer/counter that can operate as either a timer or an event counter. the type of operation is selected by bit c/t2 in the sfr t2con (shown in table 2). timer 2 has three operating modes: capture, auto-reload (up or down counting), and baud rate generator. the modes are selected by bits in t2con, as shown in table 3. timer 2 consists of two 8-bit registers, th2 and tl2. in the timer function, the tl2 register is incremented every machine cycle. since a machine cycle consists of 12 oscil- lator periods, the count rate is 1/12 of the oscillator fre- quency. in the counter function, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, t2. in this function, the external input is sampled during s5p2 of every machine cycle. when the samples show a high in one cycle and a low in the next cycle, the count is incremented. the new count value appears in the register during s3p1 of the cycle following the one in which the transition was detected. since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0 transi- tion, the maximum count rate is 1/24 of the oscillator fre- quency. to ensure that a given level is sampled at least once before it changes, the level should be held for at least one full machine cycle. capture mode in the capture mode, two options are selected by bit exen2 in t2con. if exen2 = 0, timer 2 is a 16 bit timer or counter which upon overflow sets bit tf2 in t2con. this bit can then be used to generate an interrupt. if exen2 = 1, timer 2 performs the same operation, but a 1- to-0 transition at external input t2ex also causes the cur- rent value in th2 and tl2 to be captured into rcap2h and rcap2l, respectively. in addition, the transition at t2ex causes bit exf2 in t2con to be set. the exf2 bit, like tf2, can generate an interrupt. the capture mode is illus- trated in figure 1. auto-reload (up or down counter) timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload mode. this feature is invoked by the dcen (down counter enable) bit located in the sfr t2mod (see table 4). upon reset, the dcen bit is set to 0 so that timer 2 will default to count up. when dcen is set, timer 2 can count up or down, depending on the value of the t2ex pin. figure 2 shows timer 2 automatically counting up when dcen = 0. in this mode, two options are selected by bit exen2 in t2con. if exen2 = 0, timer 2 counts up to 0ffffh and then sets the tf2 bit upon overflow. the over- flow also causes the timer registers to be reloaded with the 16 bit value in rcap2h and rcap2l. the values in rcap2h and rcap2l are preset by software. if exen2 = table 3. timer 2 operating modes rclk + tclk cp/rl2 tr2 mode 0 0 1 16 bit auto-reload 0 1 1 16 bit capture 1 x 1 baud rate generator x x 0 (off) figure 1. timer 2 in capture mode
at89c55 4-176 1, a 16 bit reload can be triggered either by an overflow or by a 1-to-0 transition at external input t2ex. this transition also sets the exf2 bit. both the tf2 and exf2 bits can generate an interrupt if enabled. setting the dcen bit enables timer 2 to count up or down, as shown in figure 3. in this mode, the t2ex pin controls the direction of the count. a logic 1 at t2ex makes timer 2 count up. the timer will overflow at 0ffffh and set the tf2 bit. this overflow also causes the 16 bit value in rcap2h and rcap2l to be reloaded into the timer regis- ters, th2 and tl2, respectively. a logic 0 at t2ex makes timer 2 count down. the timer underflows when th2 and tl2 equal the values stored in rcap2h and rcap2l. the underflow sets the tf2 bit and causes 0ffffh to be reloaded into the timer registers. the exf2 bit toggles whenever timer 2 overflows or underflows and can be used as a 17th bit of resolution. in this operating mode, exf2 does not flag an interrupt. figure 2. timer 2 auto reload mode (dcen = 0) table 4 . t2modtimer 2 mode control register t2mod address = 0c9h reset value = xxxx xx00b not bit addressable t20edcen bit 7 6 543210 symbol function not implemented, reserved for future use. t20e timer 2 output enable bit. dcen when set, this bit allows timer 2 to be configured as an up/down counter.
at89c55 4-177 figure 3. timer 2 auto reload mode (dcen = 1) osc exf2 tf2 t2ex pin count direction 1=up 0=down t2 pin tr2 control overflow (down counting reload value) (up counting reload value) toggle timer 2 interrupt 12 rcap2l rcap2h 0ffh 0ffh th2 tl2 c/t2 = 0 c/t2 = 1 figure 4. timer 2 in baud rate generator mode
at89c55 4-178 baud rate generator timer 2 is selected as the baud rate generator by setting tclk and/or rclk in t2con (table 2). note that the baud rates for transmit and receive can be different if timer 2 is used for the receiver or transmitter and timer 1 is used for the other function. setting rclk and/or tclk puts timer 2 into its baud rate generator mode, as shown in figure 4. the baud rate generator mode is similar to the auto-reload mode, in that a rollover in th2 causes the timer 2 registers to be reloaded with the 16 bit value in registers rcap2h and rcap2l, which are preset by software. the baud rates in modes 1 and 3 are determined by timer 2s overflow rate according to the following equation. the timer can be configured for either timer or counter operation. in most applications, it is configured for timer operation (cp/t2 = 0). the timer operation is different for timer 2 when it is used as a baud rate generator. normally, as a timer, it increments every machine cycle (at 1/12 the oscillator frequency). as a baud rate generator, however, it increments every state time (at 1/2 the oscillator fre- quency). the baud rate formula is given below. where (rcap2h, rcap2l) is the content of rcap2h and rcap2l taken as a 16 bit unsigned integer. timer 2 as a baud rate generator is shown in figure 4. this figure is valid only if rclk or tclk = 1 in t2con. note that a rollover in th2 does not set tf2 and will not gener- ate an interrupt. note too, that if exen2 is set, a 1-to-0 transition in t2ex will set exf2 but will not cause a reload from (rcap2h, rcap2l) to (th2, tl2). thus when timer 2 is in use as a baud rate generator, t2ex can be used as an extra external interrupt. note that when timer 2 is running (tr2 = 1) as a timer in the baud rate generator mode, th2 or tl2 should not be read from or written to. under these conditions, the timer is incremented every state time, and the results of a read or write may not be accurate. the rcap2 registers may be read but should not be written to, because a write might overlap a reload and cause write and/or reload errors. the timer should be turned off (clear tr2) before accessing the timer 2 or rcap2 registers. modes 1 and 3 baud rates timer 2 overflow rate 16 ----------------------------------------------------------- - = modes 1 and 3 baud rate --------------------------------------- oscillator frequency 32 655536 rcap2h,rcap2l ) ( C [] -------------------------------------------------------------------------------------------------- = figure 5. timer 2 in clock-out mode
at89c55 4-179 programmable clock out a 50% duty cycle clock can be programmed to come out on p1.0, as shown in figure 5. this pin, besides being a regu- lar i/o pin, has two alternate functions. it can be pro- grammed to input the external clock for timer/counter 2 or to output a 50% duty cycle clock ranging from 61 hz to 4 mhz at a 16 mhz operating frequency. to configure the timer/counter 2 as a clock generator, bit c/t2 (t2con.1) must be cleared and bit t2oe (t2mod.1) must be set. bit tr2 (t2con.2) starts and stops the timer. the clock-out frequency depends on the oscillator fre- quency and the reload value of timer 2 capture registers (rcap2h, tcap2l), as shown in the following equation: in the clock-out mode, timer 2 roll-overs will not generate an interrupt. this behavior is similar to when timer 2 is used as a baud-rate generator. it is possible to use timer 2 as a baud-rate generator and a clock generator simulta- neously. note, however, that the baud-rate and clock-out frequencies cannot be determined independently from one another since they both use rcap2h and rcap2l. uart the uart in the at89c55 operates the same way as the uart in the at89c51 and at89c52. for further informa- tion, see the microcontroller data book, section titled, serial interface. interrupts the at89c55 has a total of six interrupt vectors: two exter- nal interrupts (int0 and int1 ), three timer interrupts (tim- ers 0, 1, and 2), and the serial port interrupt. these inter- rupts are all shown in figure 6. each of these interrupt sources can be individually enabled or disabled by setting or clearing a bit in special function register ie. ie also contains a global disable bit, ea, which disables all interrupts at once. note that table 5 shows that bit position ie.6 is unimple- mented. in the at89c51 and at89lv51, bit position ie.5 is also unimplemented. user software should not write 1s to these bit positions, since they may be used in future at89 products. timer 2 interrupt is generated by the logical or of bits tf2 and exf2 in register t2con. neither of these flags is cleared by hardware when the service routine is vectored to. in fact, the service routine may have to determine whether it was tf2 or exf2 that generated the interrupt, and that bit will have to be cleared in software. ta bl e 5 . interrupt enable (ie) register figure 6. interrupt sources the timer 0 and timer 1 flags, tf0 and tf1, are set at s5p2 of the cycle in which the timers overflow. the values are then polled by the circuitry in the next cycle. however, clock-out frequency oscillator frequency 4 655536 rcap2h,rcap2l) ( C [] ---------------------------------------------------------------------------------------------- = (msb) (lsb) ea et2 es et1 ex1 et0 ex0 enable bit = 1 enables the interrupt. enable bit = 0 disables the interrupt. symbol position function ea ie.7 disables all interrupts. if ea = 0, no interrupt is acknowledged. if ea = 1, each interrupt source is individually enabled or disabled by setting or clearing its enable bit. ie.6 reserved. et2 ie.5 timer 2 interrupt enable bit. es ie.4 serial port interrupt enable bit. et1 ie.3 timer 1 interrupt enable bit. ex1 ie.2 external interrupt 1 enable bit. et0 ie.1 timer 0 interrupt enable bit. ex0 ie.0 external interrupt 0 enable bit. user software should never write 1s to unimplemented bits, because they may be used in future at89 products.
at89c55 4-180 the timer 2 flag, tf2, is set at s2p2 and is polled in the same cycle in which the timer overflows. for further infor- mation, see the microcontroller data book, section titled interrupts. oscillator characteristics xtal1 and xtal2 are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator, as shown in figure 7. either a quartz crystal or ceramic resonator may be used. to drive the device from an external clock source, xtal2 should be left unconnected while xtal1 is driven, as shown in figure 8. there are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maxi- mum voltage high and low time specifications must be observed. idle mode in idle mode, the cpu puts itself to sleep while all the on- chip peripherals remain active. the mode is invoked by software. the content of the on-chip ram and all the spe- cial functions registers remain unchanged during this mode. the idle mode can be terminated by any enabled interrupt or by a hardware reset. note that when idle mode is terminated by a hardware reset, the device normally resumes program execution from where it left off, up to two machine cycles before the internal reset algorithm takes control. on-chip hardware inhibits access to internal ram in this event, but access to the port pins is not inhibited. to eliminate the possibility of an unexpected write to a port pin when idle mode is termi- nated by a reset, the instruction following the one that invokes idle mode should not write to a port pin or to exter- nal memory. figure 7. oscillator connections note: c1,c2 = 30 pf for crystals = 40 pf for ceramic resonators figure 8 . external clock drive configuration status of external pins during idle and power down modes mode program memory ale psen port0 port1 port2 port3 idle internal 1 1 data data data data idle external 1 1 float data address data power down internal 0 0 data data data data power down external 0 0 float data data data
at89c55 4-181 power down mode in the power down mode, the oscillator is stopped, and the instruction that invokes power down is the last instruction executed. the on-chip ram and special function regis- ters retain their values until the power down mode is termi- nated. the only exit from power down is a hardware reset. reset redefines the sfrs but does not change the on-chip ram. the reset should not be activated before v cc is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and sta- bilize. program memory lock bits the at89c55 has three lock bits that can be left unpro- grammed (u) or can be programmed (p) to obtain the addi- tional features listed in the following table. when lock bit 1 is programmed, the logic level at the ea pin is sampled and latched during reset. if the device is pow- ered up without a reset, the latch initializes to a random value and holds that value until reset is activated. the latched value of ea must agree with the current logic level at that pin in order for the device to function properly. lock bit protection modes programming the flash the at89c55 is normally shipped with the on-chip flash memory array in the erased state (that is, contents = ffh) and ready to be programmed. the programming interface accepts either a high-voltage (12-volt) or a low-voltage (v cc ) program enable signal. the low voltage programming mode provides a convenient way to program the at89c55 inside the users system, while the high-voltage program- ming mode is compatible with conventional third party flash or eprom programmers. the at89c55 is shipped with either the high-voltage or low-voltage programming mode enabled. the respective top-side marking and device signature codes are listed in following table. the at89c55 code memory array is programmed byte-by- byte in either programming mode. to program any non- blank byte in the on-chip flash memory, the entire memory must be erased using the chip erase mode. programming algorithm: before programming the at89c55, the address, data and control signals should be set up according to the flash programming mode table and figures 9 and 10. to program the at89c55, take the fol- lowing steps: 1. input the desired memory location on the address lines. 2. input the appropriate data byte on the data lines. 3. activate the correct combination of control signals. 4. raise ea /v pp to 12v for the high-voltage programming mode. 5. pulse ale/prog once to program a byte in the flash array or the lock bits. the byte-write cycle is self-timed and typically takes no more than 1.5 ms. repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached. program lock bits lb1 lb2 lb3 protection type 1 u u u no program lock features. 2puu movc instructions executed from external program memory are disabled from fetching code bytes from internal memory, ea is sampled and latched on reset, and further programming of the flash memory is disabled. 3 p p u same as mode 2, but verify is also disabled. 4 p p p same as mode 3, but external execution is also disabled. v pp = 12v v pp = 5v top-side mark at89c55 at89c55 xxxx xxxx-5 yyww yyww signature (030h) = 1eh (030h) = 1eh (031h) = 55h (031h) = 55h (032h) = ffh (032h) = 05h
at89c55 4-182 data polling: the at89c55 features data polling to indi- cate the end of a write cycle. during a write cycle, an attempted read of the last byte written will result in the com- plement of the written data on po.7. once the write cycle has been completed, true data is valid on all outputs, and the next cycle may begin. data polling may begin any time after a write cycle has been initiated. ready/busy : the progress of byte programming can also be monitored by the rdy/bsy output signal. p3.4 is pulled low after ale goes high during programming to indicate busy . p3.4 is pulled high again when programming is done to indicate ready. program verify: if lock bits lb1 and lb2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. the lock bits cannot be verified directly. verification of the lock bits is achieved by observing that their features are enabled. chip erase: the entire flash array is erased electrically by using the proper combination of control signals and by holding ale/prog low for 10 ms. the code array is written with all 1s. the chip erase operation must be executed before the code memory can be reprogrammed. reading the signature bytes: the signature bytes are read by the same procedure as a normal verification of locations 030h, 031h, and 032h, except that p3.6 and p3.7 must be pulled to a logic low. the values returned are as follows. (030h) = 1eh indicates manufactured by atmel (031h) = 55h indicates 89c55 (032h) = ffh indicates 12v programming (032h) = 05h indicates 5v programming programming interface every code byte in the flash array can be written, and the entire array can be erased, by using the appropriate combi- nation of control signals. the write operation cycle is self- timed and once initiated, will automatically time itself to completion. all major programming vendors offer worldwide support for the atmel microcontroller series. please contact your local programming vendor for the appropriate software revision. figure 9. programming the flash memory *programming address line a14 (p3.0) is not the same as the external memory address line a14 (p2.6) p1 p3.6 p2.0 - p2.5 a0-a7 addr. 0000h/4fffh see flash programming modes table 3-33 mhz a8 - a13 p0 +5v p2.7 pgm data prog v/v i h pp v i h ale p3.7 xtal2 ea rst psen xtal 1 gnd v cc at89c55 p2.6 p3.0 a14* figure 10. verifying the flash memory p1 p3.6 p2.0 - p2.5 a0-a7 addr. 0000h/4fffh see flash programming modes table 3-33 mhz a8 - a13 p0 +5v p2.7 pgm data (use 10k pullups) v i h v i h ale p3.7 xtal 2 ea rst psen xtal 1 gnd v cc at89c55 p2.6 p3.0 a14*
at89c55 4-183 flash programming modes note: 1. chip erase requires a 10-ms prog pulse. mode rst psen ale/prog ea /v pp p2.6 p2.7 p3.6 p3.7 write code data h l h/12v l h h h read code data h l h h l l h h write lock bit-1 h l h/12v hhhh bit-2 hl h/12v hhll bit-3 hl h/12v hlhl chip erase hl h/12v hlll read signature byte h l h h l l l l (1)
at89c55 4-184 flash programming and verification characteristics t a = 0c to 70c, v cc = 5.0v 10% note: 1. only used in 12-volt programming mode. symbol parameter min max units v pp (1) programming enable voltage 11.5 12.5 v i pp (1) programming enable current 1.0 ma 1/t clcl oscillator frequency 3 33 mhz t avgl address setup to prog low 48t clcl t ghax address hold after prog 48t clcl t dvgl data setup to prog low 48t clcl t ghdx data hold after prog 48t clcl t ehsh p2.7 (enable ) high to v pp 48t clcl t shgl v pp setup to prog low 10 m s t ghsl (1) v pp hold after prog 10 m s t glgh prog width 1 110 m s t avqv address to data valid 48t clcl t elqv enable low to data valid 48t clcl t ehqz data float after enable 048t clcl t ghbl prog high to busy low 1.0 m s t wc byte write cycle time 2.0 ms
at89c55 4-185 flash programming and verification waveforms - low voltage mode (v pp = 5v) flash programming and verification waveforms - high voltage mode (v pp = 12v)
at89c55 4-186 dc characteristics the values shown in this table are valid for t a = -40c to 85c and v cc = 5.0v 20%, unless otherwise noted. notes: 1. under steady state (non-transient) conditions, i ol must be externally limited as follows: maximum i ol per port pin: 10 ma. maximum i ol per 8-bit port: port 0: 26 ma, ports 1, 2, 3: 15 ma. maximum total i ol for all output pins: 71 ma. if i ol exceeds the test condition, v ol may exceed the related specification. pins are not guaranteed to sink current greater than the listed test conditions. 2. minimum v cc for power down is 2v. symbol parameter condition min max units v il input low voltage (except ea )-0.50.2 v cc - 0.1 v v il1 input low voltage (ea )-0.50.2 v cc - 0.3 v v ih input high voltage (except xtal1, rst) 0.2 v cc + 0.9 v cc + 0.5 v v ih1 input high voltage (xtal1, rst) 0.7 v cc v cc + 0.5 v v ol output low voltage (1) (ports 1, 2, 3) i ol = 1.6 ma 0.45 v v ol1 output low voltage (1) (port 0, ale, psen ) i ol = 3.2 ma 0.45 v v oh output high voltage (ports 1, 2, 3, ale, psen ) i oh = -60 m a, v cc = 5v 10% 2.4 v i oh = -25 m a 0.75 v cc v i oh = -10 m a0.9 v cc v v oh1 output high voltage (port 0 in external bus mode) i oh = -800 m a, v cc = 5v 10% 2.4 v i oh = -300 m a 0.75 v cc v i oh = -80 m a0.9 v cc v i il logical 0 input current (ports 1, 2, 3) v in = 0.45v -50 m a i tl logical 1 to 0 transition current (ports 1, 2, 3) v in = 2v, v cc = 5v 10% -650 m a i li input leakage current (port 0, ea ) 0.45 < v in < v cc 10 m a rrst reset pulldown resistor 50 300 k w c io pin capacitance test freq. = 1 mhz, t a = 25c 10 pf i cc power supply current active mode, 12 mhz 25 ma idle mode, 12 mhz 6.5 ma power down mode (2) v cc = 6v 100 m a v cc = 3v 40 m a absolute maximum ratings* operating temperature ................................. -55c to +125c *notice: stresses beyond those listed under absolute maximum ratings may cause permanent dam- age to the device. this is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. storage temperature ..................................... -65c to +150c voltage on any pin with respect to ground .....................................-1.0v to +7.0v maximum operating voltage............................................. 6.6v dc output current...................................................... 15.0 ma
at89c55 4-187 ac characteristics under operating conditions, load capacitance for port 0, ale/prog , and psen = 100 pf; load capacitance for all other outputs = 80 pf. external program and data memory characteristics symbol parameter variable oscillator units min max 1/t clcl oscillator frequency 0 33 mhz t lhll ale pulse width 2t clcl - 40 ns t avll address valid to ale low t clcl - 13 ns t llax address hold after ale low t clcl - 20 ns t lliv ale low to valid instruction in 4t clcl - 65 ns t llpl ale low to psen low t clcl - 13 ns t plph psen pulse width 3t clcl - 20 ns t pliv psen low to valid instruction in 3t clcl - 45 ns t pxix input instruction hold after psen 0ns t pxiz input instruction float after psen t clcl - 10 ns t pxav psen to address valid t clcl - 8 ns t aviv address to valid instruction in 5t clcl - 55 ns t plaz psen low to address float 10 ns t rlrh rd pulse width 6t clcl - 100 ns t wlwh wr pulse width 6t clcl - 100 ns t rldv rd low to valid data in 5t clcl - 90 ns t rhdx data hold after rd 0ns t rhdz data float after rd 2t clcl - 28 ns t lldv ale low to valid data in 8t clcl - 150 ns t avdv address to valid data in 9t clcl - 165 ns t llwl ale low to rd or wr low 3t clcl - 50 3t clcl + 50 ns t avwl address to rd or wr low 4t clcl - 75 ns t qvwx data valid to wr transition t clcl - 20 ns t qvwh data valid to wr high 7t clcl - 120 ns t whqx data hold after wr t clcl - 20 ns t rlaz rd low to address float 0 ns t whlh rd or wr high to ale high t clcl - 20 t clcl + 25 ns
at89c55 4-188 external program memory read cycle external data memory read cycle
at89c55 4-189 external data memory write cycle external clock drive waveforms external clock drive symbol parameter min max units 1/t clcl oscillator frequency 0 33 mhz t clcl clock period 30 ns t chcx high time 12 ns t clcx low time 12 ns t clch rise time 20 ns t chcl fall time 20 ns
at89c55 4-190 shift register mode timing waveforms ac testing input/output waveforms (1) note: 1. ac inputs during testing are driven at v cc - 0.5v for a logic 1 and 0.45v for a logic 0. timing measurements are made at v ih min. for a logic 1 and v il max. for a logic 0. float waveforms (1) note: 1. for timing purposes, a port pin is no longer floating when a 100 mv change from load volt- age occurs. a port pin begins to float when a 100 mv change from the loaded v oh /v ol level occurs. serial port timing: shift register mode test conditions the values in this table are valid for v cc = 5.0v 20% and load capacitance = 80 pf. symbol parameter min max units t xlxl serial port clock cycle time 12t clcl ns t qvxh output data setup to clock rising edge 10t clcl - 133 ns t xhqx output data hold after clock rising edge 2t clcl - 117 ns t xhdx input data hold after clock rising edge 0 ns t xhdv clock rising edge to input data valid 10t clcl - 133 ns
at89c55 4-191 notes: 1. xtal1 tied to gnd for i cc (power down) 2. lock bits programmed
at89c55 4-192 ordering information speed (mhz) power supply ordering code package operation range 16 5v 20% at89c55-16aa at89c55-16ja at89c55-16pa at89c55-16qa 44a 44j 40p6 44q automotive (-40 c to 105 c) 24 5v 20% at89c55-24ac at89c55-24jc at89c55-24pc at89c55-24qc 44a 44j 40p6 44q commercial (0 c to 70 c) at89c55-24ai at89c55-24ji AT89C55-24PI at89c55-24qi 44a 44j 40p6 44q industrial (-40 c to 85 c) 33 5v 10% at89c55-33ac at89c55-33jc at89c55-33pc at89c55-33qc 44a 44j 40p6 44q commercial (0 c to 70 c) package type 44a 44 lead, thin plastic gull wing quad flatpack (tqfp) 44j 44 lead, plastic j-leaded chip carrier (plcc) 40p6 40 lead, 0.600" wide, plastic dual inline package (pdip) 44q 44 lead, plastic gull wing quad flatpack (pqfp)

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