GE 90-30/20/Micro manual Sweep Description Time Contribution ms Element, Calculate sweep time

2

As shown in the PLC sweep sequence, several items are included in the sweep. These items contribute to the total sweep time as shown in the following table.

Table 2-1. Sweep Time Contribution

Sweep	Description	Time Contribution (ms) 4
Element
		351/352 (350 and 360 series—see note)
Housekeeping ∙	Calculate sweep time.	0.279

∙Schedule start of next sweep.

∙Determine mode of next sweep.

∙Update fault reference tables.

∙Reset watchdog timer.

Data Input	Input data is received from input and		See Table 2-2 for scan time contributions.
	option modules.
Program	User logic is solved.		Execution time is dependent upon the length of the
Execution			program and the type of instructions used in the
			program. Instruction execution times are listed in
			Appendix A.
Data Output	Output data is sent to output and option		See Table 2-2 for scan time contributions.
	modules.
Service External	Service requests from	HHP	0.334
Devices	programming devices and
	intelligent modules are
	processed. 1
		LM-90	0.517
		PCM 2	0.482
Reconfiguration	Slots with faulted modules and empty slots		0.319
	are monitored.
Diagnostics	Verify user program integrity		0.010 per word checksummed each sweep3

1.The scan time contribution of external device service is dependent upon the mode of the communications

window in which the service is processed. If the window mode is LIMITED, a maximum of 8 milliseconds for the 311, 313, 323, and 331 CPUs and 6 milliseconds for the 340 and higher CPUs will be spent during that window. If the window mode is RUN-TO-COMPLETION, a maximum of 50 ms can be spent in that window, depending upon the number of requests which are presented simultaneously.

2.These measurements were taken with the PCM physically present but not configured and with no application task running on the PCM.

3.The number of words checksummed each sweep can be changed with the SVCREQ function block.

4.These measurements were taken with an empty program and the default configuration. The Series 90-30

PLCs were in an empty 10-slot rack with no extension racks connected. Also, the times in this table assume that there is no periodic subroutine active; the times will be larger if a periodic subroutine is active.

5.The data input time for the Micro PLC can be determined as follows: 0.365 ms. (fixed scan) + 0.036 ms. (filter time) x

(total sweep time)/0.5 ms.

6.Since the Micro PLC has a static set of I/O, reconfiguration is not necessary.

7.Since the user program for the Micro PLC is in Flash memory, it will not be checked for integrity.

Note

The times for the 350 CPU and the 360 series are estimated to be the same.

2-4 Series 90-30/20/Micro Programmable Controllers Reference Manual– September 1998 GFK-0467K