
IBM3206K0424
Preliminary
IBM Processor for Network Resources
pnr25.chapt05.01
August 14, 2000
The PHY Interface (LINKC)
Page 409 of 676
8
Reserved
Reserved
7-0
Bits 7-0 only have meaning if a PMC PM5346 SUNI LITE/UTOPIA (bits 15-13 = "011") is selected. Otherwise, they are 
ignored. Bits 2-0 are used to make adjustments to the Utopia interface for compatibility with the Suni-PHD PHY.
7
Byte Cell
When set, the cell received from the PHY will be 52 bytes. No HEC byte will be 
received.
6-5
Reserved
Reserved
6
Unassigned/Idle Cell Reception
When set to 
’
1
’
, this bit will enable unassigned/idle cell reception. This should be set to 
’
0
’
 when using the internal SONET Framer.
5
Disable Limited HEC Checking on 
Received Idle/Unassigned Cells
If bit 5 is set to 
’
1
’
, the receive logic will ignore the HEC byte of the header of idle and 
unassigned cells. Idle is defined as a header of X'00000001' and unassigned is defined 
as a header of X'0000000n' where n is 'xxx0'. If bit 6 is set to enable unassigned/idle 
cell reception, all cells will be passed to REASM regardless of how this bit is set. If bit 6 
is set to disable unassigned/idle cell reception and this bit is set to 
’
0
’
, the HEC byte of 
cells with an apparent idle header will be completely checked before deciding whether 
or not to pass the cell to REASM. If a cell appears to have an unassigned header, HEC 
bits 7, 6, and 0 will be checked because they are a constant, regardless of the value of 
bits 3, 2, and 1 of the header. If other HEC bits are bad, REASM will detect the HEC 
error and discard the cell. If there is a correctable HEC error and the cell is indeed 
unassigned, an out of range error will occur in REASM.
4
Ignore GFC in Null/Idle Cell Deter-
mination
Bit 4, when set, will cause the receive logic to ignore the first four bits of the ATM 
header in determining whether a cell being received is a null or idle cell.
3
Enable XON/XOFF
Bit 3, when set, will allow the XON/XOFF bit of the header of a received cell to sus-
pend/continue transmission from the IBM3206K0424's transmit logic for all ports asso-
ciated with Config 0.
2
Drive RENB Inactive When Not 
Receiving
When set to 
’
1
’
, this bit forces the receive logic to deactivate RENB when in the idle 
state.
1
Gate RSOC with RCA
When set to 
’
1
’
, this bit forces the receive logic to see both RSOC and RCA before 
considering RSOC valid.
0
Receive Extra Header Byte
When set to 
’
1
’
, this bit allows an extra header byte to be accepted at the start of a cell 
by the receive logic. The extra byte is discarded.
Bit(s)
Name
Description