Mitsubishi Electronics 13JW55 ユーザーズマニュアル

 

 

App. - 3

 

 

 
Appendix 1.3    Comparisons between the direct mode and refresh mode 

In the example ladder given below, turning on input X0 turns on output Y70. 

 

Item 

Direct mode 

Refresh mode 

1. Ladder example 

Y70

DX0

 

Y70

X0

 

 

END

Internal input

Input instruction (LD X0)

Output instruction (OUT Y70)

Program execution

0

Minimum delay

Maximum delay

X0

X0

Y70

Y70

0

END

0

Delay

(One scan)

Delay

(Two scans)

Input refresh
Output refresh

Internal input

2. Response lag 

from when input 

is changed to 

when output is 

changed 

accordingly 

 

END

END

Delay

(One scan)

Delay 
(execution time of the instruction)

Input instruction (LD X0)

Output instruction (OUT Y70)

Program execution

0

0

0

0

Minimum delay

Maximum delay

X0

Y70

X0

Y70

 

 

•  The delay time ranges from 0 (only execution 

time of the instruction) to 1 scan. 

•  The delay time is 0 to 1 scan. 

•  The delay time ranges from 1 to 2 scans. 

•  The delay time is 1 to 2 scans. 

3. Execution time 

of the I/O 

instruction 

•  The direct mode needs longer time than the 

refresh mode since a programmable controller 

accesses I/O modules. 

•  Generally, only short time is needed since a 

programmable controller accesses data 

memory. 

4. Scan time 

•  The scan time is longer for the execution time 

of the I/O instructions. 

•  The actual scan time is the program execution 

time. 

•  The scan time is shorter for the execution time 

of the I/O instructions. 

•  The actual scan time is the total time of a 

program execution, input transfer, and output 

transfer.