application note st10 with mac ? 7096464 a 5, nov 1998 direct memory access using mac direct memory access uses the st10 mac for address generation in external memory-external memory transfers. this application note supplies the machine code for external memory - st10 internal memory transfers, and for external memory-external memory transfers made by direct memory access using the mac. for reference, the st10 long addressing mode is summarized. the st10 instruction set contains special mac instructions and two new addressing modes which supply the mac with up to 2 new operands per instruction. the mac contains a 16x16 multiplier, 40 bit accumulator a repeat unit and an address generator. figure 1 system overview memory 1 memory 2 dual port ram (internal) internal memory (flash or dram) st10 with mac external bus
direct memory access using mac 7096464 a 2/5 1 memory transfer to st10 internal memory this machine code writes from external memory to internal memory, using the internal bus (stand-alone or super integrated). it is not possible to execute code residing in the st10 internal memory, while writing into it. the code below, must resides in another memory, e.g. external memory, x-memory, dpram. mov dppx, #addr_source ; 10 bit prefix to point source memory mov dppx, #addr_dest ; 10 bit prefix to point destination memory mov r0, #addr_beg_source ; 14 lsw of the address where to copy mov r1, #addr_beg_dest ; 14 lsw of the address destination mov r3, #addr_end_source ; 14 lsw of the last address to transfer ; note that it can be done with a block size ; instead of a given address. mov r2, [r0+] ; perform the copy from (r0) to r2 ; then increment the r0 register by 2. mov [r1+], r2 ; perform the copy from r2 to (r1). ; then increment the r1register by 2. cmp r0, r3 ; compare current address (r0) to end address ; (r3). loop until r0 >r3. ; note that this test can be done for a given ; count. jmpr cc_ule, loop ret ; return, or reti if done under interrupt
direct memory access using mac 3/5 7096464 a 2 memory transfer to external memory this machine code writes from one external memory to another external memory, using direct memory access with mac address generation.. dma timing analysis for a 50 mhz st10 using a 16-bit wide demux bus: ? register set-up takes 400 ns and only has to be done once. ? the first memory access takes 80ns. each subsequent memory access takes 40 ns. note this program only takes into account the program execution time and the time taken for memory accesses (including any waitstates on the source and the destination memory). mov dppx, #xxxx ; 10 bit prefix to point source memory mov dppx, #xxxx ; 10 bit prefix to point destination memory ; solution if a 8 bit wide bus is used ; (3 lines below) extr #2 ; two following instructions used esfr space mov qx0, #1 ; store 1 in qx0 to allow byte transfers mov qr0, #1 ; store 1 in qr0 to allow byte transfers mov idx0, #dest ; 14 lsw of the address where to copy mov r0, #source ;14 lsw of the address source mov mrw, #repeat ; use the maximum repeat depending on the ; timings allowed to perform copies ; solution if a 16 bit wide bus is used repeat mrw times comov [idx0+], [r0+] ; perform the copy from (r0) to (idx0) ; then increment the two registers by 2. ret ; return or reti if done under interrupt
direct memory access using mac 7096464 a 4/5 3 long addressing mode summary the long addressing mode uses one of the four dpp registers to specify a physical 18-bit or 24-bit address. long 16-bit addresses are treated in two parts. bits 0...13 specify the 14-bit data page offset, and bits 15...14 specify the data page pointer (1 of 4). the lower ten bits of the selected dpp register are concatenated with the 14-bit data page offset to generate the physical 24-bit address (see figure below). the following address values are used: 00= dpp0, 01 = dpp1, 10 = dpp2, 11 = dpp3. using the value 0x8c00 for addr_beg_source, the two msb are 10. therefore, ddp2 is used. if dpp2 = 0x0030, the resulting physical address is 0xc0c00. figure 2 interpretation of a 16-bit long address 0 15 14 13 16-bit long address dpp0 dpp1 dpp2 dpp3 14-bit page offset 24-bit physical address selects data page pointer 0 9 0 23 13 14
direct memory access using mac 5/5 7096464 a information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specifications mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicroelectronics. the st logo is a trademark of stmicroelectronics ? 1998 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - brazil - canada - china - france - germany - italy - japan - korea - malaysia - malta - mexico - morocco the netherlands - singapore - spain - sweden - switzerland - taiwan - thailand - united kingdom - u.s.a. http ://www.st.com
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