5 Operation
5-40
CJ-series PROFIBUS Master Unit Operation Manual for NJ-series CPU Unit (W509)
The total I/O response time is the sum of all components:
T
IO
= T
IN
+ T
PB,Cyc
+ 2*T
M,Proc
+ T
M,Rrf
+ T
CPU,Cyc
+ T
CPU,Rf
+ T
OUT
Startup Time Definition
The system startup time is the delay from the time the CJ1W-PRM21 PROFIBUS Master Unit is
turned ON, or reset, until I/O data exchange with all slave devices has been established. For this,
the following is assumed:
• The Master Unit has been configured to go to OPERATE mode if the CPU mode is set to RUN
mode.
• All slave devices are powered up and initialized before the Master Unit is turned ON.
• All slave devices are assumed to go to I/O data exchange without delays.
The total system startup time is the sum of the following components:
• Master Unit startup checking.
• Initialization of communication with CPU CPU.
• Master Unit I/O configuration initialization after which the Master Unit goes to OPERATE.
• One PROFIBUS DP cycle to request slave diagnostics.
• One PROFIBUS DP cycle to transmit parameter messages to all slave devices.
• One PROFIBUS DP cycle to transmit the I/O configuration messages to all slave devices.
• One PROFIBUS DP cycle to request slave diagnostics.
The average time for the first three actions - assuming a maximum I/O configuration - is approxi-
mately 2 seconds. The remaining time depends on the PROFIBUS settings.
For a maximum I/O configuration, with 125 slave devices, 56 words I/O each, (i.e. the total I/O size
amounts up to 7000 words) one PROFIBUS DP cycle lasts approximately 70 ms. A complete start
up cycle will then last approximately 280 ms.
The total system start up time, from Unit reset until I/O data exchange, will then be 2.3 seconds.
• The NJ-series Controller CPU requires 10 to 20 seconds to start.
• It is recommended to program fail-safe circuits or use effective flags.
5-5-6 System Startup Time
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