Bradley Smoker PLC-5 Calculating Block-Transfer Completion Time, Where, This formula assumes

Communicating with Extended-Local I/O 8-7

This formula assumes:

block-transfer instructions are consecutively placed in the logic program

block-transfer modules in the I/O chassis are ready to perform when operations are requested

This formula assumes:

block-transfer instructions are consecutively placed in the logic program

block-transfer modules in the I/O chassis are ready to perform when operations are requested

Calculating Block-Transfer Completion Time

You can calculate two types of block-transfer timing:

•worst-case calculation for the completion of all block-transfers in the system

•the time to perform a block-transfer for any one block-transfer module in the system

Calculating Worst-Case Completion Time

block-transfer duration (ms) = D R

D = 2E L + (0.1W)and		logic scan + housekeeping
	R =
		logic scan
	or
where:	R = 1 (when D < logic scan time)

E= number of extended-local I/O chassis with block-transfer modules

L= largest number of block-transfer modules in any extended-local I/O chassis

W = number of words in the longest block-transfer request

Calculating Completion Time for any One Block-Transfer

block-transfer duration (ms) = D R

D = [2E M + (0.1W)]and		logic scan + housekeeping
	R =
		logic scan
	or
where:	R = 1 (when D < logic scan time)

E= number of extended-local I/O chassis with 1771-ALX adapter modules and block-transfer modules

M = number of block-transfer modules in the chassis of the module being calculated

W= number of words in block-transfer request being calculated

Publication 1785-UM012D-EN-P - July 2005