Reference Guide

ZCOM Tables and Data Structures
Interface Table
Chapter 394
Each element of the subchannel specification array has the following
structure:
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
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)