ZCOM Tables and Data Structures

Interface Table

Each element of the subchannel specification array has the following structure:

Table 3-23 Subchannel Specification Array Element Structure

31-30

29-24

23-8

7

6-3

2-1

0

 

 

 

 

 

 

 

spare

ITBS

spare

INV

spare

mode

spare

 

 

 

 

 

 

 

 

ITBS

-

Individual Transmit Buffer Size

 

 

INV

-

Inversion flag

 

 

 

mode

-

Transmission mode

 

 

 

spare

-

Reserved, not used (must be 0)

 

IFIRQBP, IRESPBP, ISTDTBP - DMA reply buffer pointers (char *)

These fields point to the corresponding buffers kept at the end of the interface table that are used by the DAM for DMA operations. The actual values of these pointers are initialized at ZCOM subsystem initialization time by the LDM. These pointers are chosen by the LDM so that each buffer is 64-byte aligned. (The buffers must be aligned so that the DMA may read/write directly to them). These fields are not used for ACC E1/T1 cards.

IFPNTR - Pointer to active physical terminal table

This field contains the address of the currently active physical terminal table entry within this interface table. This field is not used for ACC E1/T1 cards It is maintained by the DAM.

IFCMDBUF - Current backplane command buffer

This field is the buffer area for DMA transfer of a backplane command to the Mux interface card. The actual area being used is offset by the number of bytes specified in IFBOFF. This area is accessed by the pointer field IFCMDBP.

IFIRQBUF, IRESPBUF, ISTDTBUF - DMA response buffers

These are response buffers that are written to by DMA read requests to the Mux interface card. The FIRQ buffer contains the results of an $FIRQ backplane transaction. The Response buffer contains the response that provides the DAM with the completion status from the

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Chapter 3