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Definitions of R_LOG, R_ID, W_LOG and W_ID:

R_LOG:
      -	Credit value for out-going credit cell if the current R_IVC is
	a credit cell. (R_NULL=1 in this case).
      -	B7=(credit==0), B6-B0=(upper 7 bits of cell count) if the current
	R_IVC is a data cell (R_NULL=0 in this case).
      -	Undefined if the current R_IVC is an idle cell.

R_ID:
	0	R_IVC is a data cell or an "normal idle";
	1	R_IVC is a credit cell;
	2	Status bits disabled by LF_CNT, TX_FF, _FORCEIDLE, or DIS_STA
		Note that the current R_IVC may not be an idle.
	3	R_IVC is a null due to a CLM dequeue error;
	4	R_IVC is a null due to an ALM dequeue error;

W_LOG:
	If W_IVC is a credit cell, W_LOG is the current uncorrected credit
	value from the cell.
	If W_IVC is a data cell, W_LOG is the Bcnt of W_IVC.
	If W_IVC is an idle cell, W_LOG is undefined.
	
W_ID:
     B2:
	0	Last W_IVC did not have CRC-32 error
	1	Last W_IVC had CRC-32 error
     B1-B0:
	0	W_IVC is a data cell;
	1	W_IVC is a credit cell;
	2	W_IVC is a null due to a HEC error;
	3	W_IVC is a null due to a drop in the CM;
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