28500-PBD-001-B
October 2006
CX28500
Product Bulletin
Products Affected: CX28500-11P, CX28500-12P
This document describes conditions that may cause the operation of the above device to deviate from published
specifications.
Possible Miscalculation of Frame Check Sequence (FCS) in Transmit
Direction When Pad Count is Less than Two or Pad Adjust is Enabled
Description:
For channels configured in HDLC FCS-16 or FCS-32 modes, the FCS may be incorrectly calculated in the transmit
direction when the Pad Count is less than two, or the Pad Adjust is enabled.
Recommended Action:
1. Use Pad Count >= 2
and
2. Disable Pad Adjust.
Pad Count is set in the transmitted buffer descriptor (only for the last buffer in a message), in bits 25:18.
Pad Adjust is disabled by clearing bit #2 (TPADJ) in the TSLP Channel Configuration Register
(address 11000h + 4 * channel number).
The relative amount of bandwidth left unexploited by using this method is at most 4.44% for 40-byte packets.
28500-PBD-001-B
Mindspeed Technologies
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CX28500 Product Bulletin
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28500-PBD-001-B
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