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PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
OOF Generation For Devices Using Edge Sensitive Byte Alignment Algorithms.
Preliminary Issue 2: Oct, 1996
PMC-Sierra, Inc.
105 - 8555 Baxter Place, Burnaby, BC Canada, V5A 4V7. 604 415 6000
PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
TABLE OF CONTENTS OOF Generation Circuit For Devices Expecting An Edge Sensitive Input .......... 1 List of PMC-Sierra Components Affected ........................................................... 3 References ......................................................................................................... 4
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PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
OOF GENERATION CIRCUIT FOR DEVICES EXPECTING AN EDGE SENSITIVE INPUT The edge sensitive OOF input of the SIPO Device is incompatible with the PM5355 S/UNI-622's level sensitive OOF output. The SIPO expects a rising edge on its OOF input to trigger the search for a valid byte alignment. In case of a received frame mimic pattern the SIPO can lock on to an invalid frame alignment (generated by a mimic framing pattern). In this case the PM5355 will not go into frame and will continue to assert its OOF output. In order for the SIPO to trigger again to find the real frame alignment a second rising edge is required on its OOF input. Since the PM5355 does not generate a second rising edge, the circuit illustrated in Figure 1 must be implemented. Figure 1: Revised OOF Generation Circuit
SIPO DEVICE
D D Q Q CL Q Q OOF DXCK FP DXDT[7:0]
PM5355 S/UNI-622
PICLK FPIN PIN[7:0] OOF OHFP
Revised applications solution introduces 2 D Flip-Flops
A previous OOF generation circuit, consisting of a logical AND of the OOF and OHFP outputs of the PM5355 connected to the OOF input of the SIPO, did not account for the possibility of the OHFP signal going high while a valid framing sequence was being processed by the SIPO Device. This action, illustrated in Figure 2, did not allow the system to find frame because an OOF rising edge was generated on the SIPO's OOF input when a valid frame was detected.
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PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
Figure 2: Result of OHFP Assertion During Valid Frame Sequence
A1/A2
OOF input
A1/A2
A1
A1
A1
A1
A1
A1
A1
A1
A1
A1
A1
A1
A2
A2
A2
A2
A2
A2
A2
A2
A2
A2
A2
A2
* rising OOF edge occuring anywhere in this range causes SIPO Device to begin search for 3xA1 and 3xA2 * 3 consecutive A1's seen almost 1 frame later (first 3 of string of 12 A1's), search begins for A2's * next rising OOF edge before occurrence of A2's causes search to restart for A1's.
The new circuitry solves the above problem by pulsing the SIPO's OOF input every other time. The timing of the revised circuitry is illustrated in Figure 3. Figure 3: OOF Timing with new circuitry
A1/A2
OOF input
A1/A2
A1/A2
rising OOF edge occuring anywhere in this range causes SIPO Device to begin search for 3xA1 and 3xA2
* 3 consecutive A1's seen almost 1 frame later (first 3 of string of 12 A1's), search begins for A2's *3xA2's found, byte-alignment is declared and S/UNI-622 receive timeslot counter is reset; ready to validate framing pattern one frame later
* S/UNI-622 validates current byte-alignment * deasserts OOF 125sec later (dotted rising edge corresponds to next rising OOF edge if byte alignment had failed)
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PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
LIST OF PMC-SIERRA COMPONENTS AFFECTED All PMC-Sierra PHY layer devices have a level sensitive OOF output. The specific OC-12 components that may be affected are: 1. PM5355 S/UNI-622 2. PM5312 STTX - note that the illustrations above may be used to describe an applications solution for the STTX. In the case of the STTX, substitute the STTX for the S/UNI-622 and substitute ROFP for OHFP.
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PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
REFERENCES 1) 2) PMC-Sierra, Inc., PM5355 S/UNI-622 Data Sheet, Issue 2, April, 1996. PMC-Sierra, Inc., PM5312 STTX Data Sheet, Issue 4, Apr 11, 1995.
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PMC-Sierra, Inc. APPLICATIONS
ISSUE 2
OOF Generation
NOTES
Seller will have no obligation or liability in respect of defects or damage caused by unauthorized use, mis-use, accident, external cause, installation error, or normal wear and tear. There are no warranties, representations or guarantees of any kind, either express or implied by law or custom, regarding the product or its performance, including those regarding quality, merchantability, fitness for purpose, condition, design, title, infringement of thirdparty rights, or conformance with sample. Seller shall not be responsible for any loss or damage of whatever nature resulting from the use of, or reliance upon, the information contained in this document. In no event will Seller be liable to Buyer or to any other party for loss of profits, loss of savings, or punitive, exemplary, incidental, consequential or special damages, even if Seller has knowledge of the possibility of such potential loss or damage and even if caused by Seller's negligence. (c) 1996 PMC-Sierra, Inc. PMC-950513 Issue date: August, 1996.
PMC-Sierra, Inc.
105 - 8555 Baxter Place, Burnaby, BC Canada, V5A 4V7. 604 415 6000

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