Specifications

5. Initial PLC Start-Up
© DELTA ELECTRONICS, INC. ALLRIGHTS RESERVED
5-2
 PLC Operation flowchart and timing
Power up
Check Hardware &
Pro
g
ram memor
y
Initialization
OK
Λ
Yes
No
Preset Watchdo
g
time
r
Mode ?
STOP
RUN
Report error,
set flag register,
turn on LED
1 2
Execute program
Check scan time
System waits until scan time
is over the set value
Update Input/Output
Check
p
eri
p
herals
Do diagnostics
OK ?
Yes
No
Report error, set flag
register, turn on LED
Force PLC into STOP mode
1 2
Low Voltage ?
No
Yes
Error LED flashing
Store data into memory
Power Good ?
No
Yes
PLC Shut down
Scan
Field input
Solve
Program
Input On/Off
Delay
Output On/Off
Delay
I/O Res
p
onse Time
CPU Writes Out
p
uts
Read
Inputs
Write
Outputs
Scan
CPU Reads In
p
uts
Solve
Program
Solve
Program
Solve
Program
In this case, you can calculate the response time by
simply adding the following items:
Input Delay + Scan Time + Output Delay = Response Time