Output registers, Commands – Delta MMC120 User Manual

Page 49

MMC120 Linear Motion Control Module

Communicating with the MMC120

Delta Computer Systems, Inc. 360/254-8688

Output Registers

Four 16-bit registers are sent to the MMC120 each time the I/O drop is accessed. The registers contain
commands and data:

Register Number

Contents

4TTTTT + 0

Command - Axis 1

4TTTTT + 1

Data Out - Axis 1

4TTTTT + 2

Command - Axis 2

4TTTTT + 3

Data Out - Axis 2

The commands sent to the two axes are independent of each other.

Data should only be written to the module once per segment, otherwise new data overwrites previous data.
Only the last information placed in the output registers is transferred to the module.

COMMANDS

Command registers are divided into two bytes. The most significant byte (bits 1 - 8) specifies the Readback
mode; it is called the READBACK byte. The least significant byte (bits 9 - 16) specifies the instruction the
MMC120 is to follow; it is called the INSTRUCTION byte.

The two bytes in the command register are divided into 4-bit nibbles (a "nibble" is half a byte). In the
INSTRUCTION byte the most significant nibble (bits 9 - 12) specifies the Command Type; the least
significant nibble (bits 13 - 16) specifies an index indicating what the command acts on. In the Readback
byte, bits 5 - 8 are the Status Area Request (SAR) field indicating what status information the MMC120 is to
return, and bits 1 - 4 are used by plots and Event Step commands. (See the Input Register section.)

Command Register

READBACK

INSTRUCTION

Events & Plots

SAR

CMD TYPE

INDEX

Bit #