Forming a “bit specific” M-Variable definition for a structure element

Summary/Issue Description

Sometimes there is a need to create an M-Variable definition for a given PMAC structure element that specifies specific bits not separately available in that element or sub element(s). This example will use “Gate3[0].Chan[1].ABC”, specifically defining the “C” bit (encoder C-channel bit). 

Root Cause

There is no structure element that specifies this specific bit alone.

Solution

Using the SRM “memory map” to find the top-level (base) address, offsets and bit location one can build the “raw” address. The “Gate3[0].Chan[1].ABC” is a partial-word element of “Gate3[0].Chan[1].Status”.

From “Power PMAC ASIC Register Element Addresses” -> “DSPGATE3 (PMAC3-Style General ASIC) Register Elements”:

The top-level base address for “Gate3[0]” is “$9000000”. The offset from base address for “Chan[1]” is “$80”. The offset from the channel base to the “Status” element is “$0”. So the “full” address is then the sum of these: “$900080”. The “C” pin is at bit 6 for a width of 1 bit.

This would “generate: the following M-variable definition: 

m99->u.io:$900080.6.1

Using the IDE’s “PMAC Project Enhanced Script Language” one can declare a pointer variable with a more functional “name”: 

ptr EncoderC-chanBit->u.io:$900080.6.1

Date/Revision History

First review 3/24/2025 V1.0

Author:

Stephen Milici, Technical Support Engineer

References

Power PMAC Software Reference Manual: https://assets.omron.com/m/76e3f5e50c46e0e9/original/Power-PMAC-Software-Reference-Manual.pdf