Program execution, Not synchronizing the high-speed scans – Yaskawa MP920 User's Manual Design User Manual

Page 431

9 Multi-CPU System

9.1.2 Operation

9-4

Program Execution

Load user application programs, such as ladder and motion programs, to both CPU Module
1 and CPU Module 2. Each CPU Module executes the programs loaded onto it indepen-
dently.

Determine the processing to be executed by each CPU Module considering the balance of
the loads on the CPU Modules and the assignments for Optional Modules (e.g., which CPU
Module is used for I/O processing), and then prepare programs for CPU Module 1 and CPU
Module 2.

The scans to be synchronized in the Multi-CPU System can be set in the System Configura-
tion Window: H/L (both high-speed and low-speed scans), Only H scan, Only L scan, or No
Synchronize. The default setting is Only H scan. For details, refer to b) of step 4 in 9.2.2
Setup Procedure Using the MPE720.

When scan synchronization (H/L, Only H scan, or Only L scan) is selected, execution of
processing starts at the same time for the specified scans. Therefore, coordinated processing
between CPU Module 1 and CPU Module 2 can be achieved. Each step in the processing,
however, is not synchronized, so it is not possible to execute specified steps in the process-
ing of CPU Module 1 and CPU Module 2 at the same time during a scan. (Refer to Fig. 9.4.)

When No Synchronize is selected, it is possible to use one CPU Module for high-speed pro-
cessing and the other CPU Module for low-speed processing.

Not Synchronizing the High-speed Scans

Fig. 9.3 CPU Module Processing Timing Example 1

CPU Module 1
High-speed
scan

CPU Module 2
High-speed
scan

I/O
pro-
cessing

Execution of ladder/
motion programs

After the execution starts with

the same scan setting (2 ms),

the processing execution

timing will differ because of

clock jitter.

2 ms