
IBM3206K0424
Preliminary
IBM Processor for Network Resources
pnr25.chapt05.01
August 14, 2000
Cell/Packet Re-assembly (REASM)
Page 351 of 676
12.30: RXAAL Transmit Queue Length Compression Configuration
This register allows the user to configure how the transmit queue lengths should be compressed for use in the 
receive packet header. CSKED provides twelve transmit queue lengths specified in bytes. A 32-bit register 
(the 
Bytes Queued Counters
 in CSKED) is available for the high, medium, and low priority queues for each of 
the four PHY ports. Using the full counts in the receive packet header generally uses too much room. This 
register allows the user to configure how this information should be compressed for use in the receive packet 
header. 
Length
4 bits
Type
Read/Write
Address
XXXX 1730
Power On Value
X
’
00000000
’
Restrictions
None
Bit(s)
Description
3-0
The following are the options:
0000
Use the full register representation for port zero only (3 - 32 bit words)
0001
Use the 2K scaled representation for port zero only (1 - 32 bit words)
0010
Use the 4K scaled representation for port zero only (1 - 32 bit words)
0011
Use the 8K scaled representation for port zero only (1 - 32 bit words)
0100
Use the 16K scaled representation for port zero only (1 - 32 bit words)
0101
Use the 32K scaled representation for port zero only (1 - 32 bit words)
0110
Use the 64K scaled representation for port zero only (1 - 32 bit words)
0111
Use the 128K scaled representation for port zero only (1 - 32 bit words)
1000
Reserved
1001
Use the 2K scaled representation for all ports (3 - 32 bit words)
1010
Use the 4K scaled representation for all ports (3 - 32 bit words)
1011
Use the 8K scaled representation for all ports (3 - 32 bit words)
1100
Use the 16K scaled representation for all ports (3 - 32 bit words)
1101
Use the 32K scaled representation for all ports (3 - 32 bit words)
1110
Use the 64K scaled representation for all ports (3 - 32 bit words)
1111
Use the 128K scaled representation for all ports. (3 - 32 bit words)
For example, using option "0001," a single 32-bit word is used. The most significant byte contains the transmit 
queue length for the high priority queue for port zero divided by 2K bytes. If the scaled count overflows (greater 
than 2K*0xff), a value of 0xff is used. The next byte contains the scaled count for the medium priority queue, 
and the third byte contains the scaled count for the low priority queue. The least significant byte is not used.
Using option "1010" three 32-bit words are used. The first word contains the scaled counts for the high priority 
queue. The second word contains the scaled counts for the medium priority queue. The third word contains the 
scaled counts for the low priority queue. Within each word, the first byte contains the scaled count for port zero, 
and the subsequent bytes are used for the other ports (1, 2, 3). The counts are divided by 4K in this case.