Delta MMC120 - Manual (Page 95)

MMC120 Linear Motion Control Module Appendix B: Event Control
Delta Computer Systems, Inc 360/254-8688 95
Appendix B: Event Control
Introduction
The Event Control feature in the MMC120 allows you to execute a sequence of commands without intervention
from the Programmable Controller (P/C). This lets the module respond to events within one millisecond rather
than the scan rate of the P/C. It also reduces the ladder logic programming required.
Overview
Event Control consists of a series of Steps which are linked together in sequences. The Steps consist of a
command area containing the instruction to be executed and a link area which specifies the next Step number
and its trigger. There are a total of 256 Steps which can be shared by both axes.
Both axes can execute any of the sequences at any time. After the Event Control Steps are configured, the
Programmable Controller need only start a Step sequence to execute a complicated motion profile. Steps in the
sequence can respond to internal conditions - positions, speeds, and status - in one millisecond rather than at
the Programmable Controller scan time.
Steps
Each Step contains a command with its associated parameters, plus the information necessary to link to the
next Step in a sequence. The Step format is as follows:
Mode Mode Word
Accel Acceleration
Decel Deceleration
Speed Requested Speed
Command Value Requested Position or command value
Command Any valid ASCII command
Link Type Condition that triggers execution of next Step
Link Value Parameter associated with Link Type
Link Next Number of next Step in sequence
Commands
Any command which can be issued by the Programmable Controller can be used in a Step.
Link Word
The Link word, which indicates the next Step to be executed (the Link Next byte), also controls when the Step
gets executed (the Link Type byte). The Link Next and Link Type bytes are stored in the two bytes of a 16 bit
word:
Link Next Link Type
(8 bits) (8 bits)
The complete Step is stored in memory in the following format: