Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 97)

Chapter 8
Block Transfer
8-7
Timing Formula
In the following formula, we assume that the module is ready to perform a
transfer when asked, as is frequently true. (If a module is not ready to
perform a BT when asked, then the time for it to get ready must be added
to the total time.
T = (Effective Number of Scans) x (Scan List Length) x (Time per Scan)
+ (Number of BTs) x (Time per BT) + ((Number of Words)
x (Time per Word))
where T is the time it takes to complete all block transfers that are queued,
given the constraints of the formula.
Effective Number of Scans: If each adapter is in the scanner’s scan list
only once, and no module has more than one BT queued to it, then the
effective number of scans is the largest number of BTs queued to any one
adapter, plus one. For complete details, see the “Number of Scans” section
below.
Scan List Length: The number of adapters in the scan list.
Time per Scan: The time required to scan an adapter depends on the baud
rate. At 57.6 Kbaud the time is 11 milliseconds. At 115.2 Kbaud the time
is 7 ms.
Number of BTs: The total number of BTs in the scanner’s queue.
Time per BT: At 57.6 Kbaud or 115.2 Kbaud the time is 5.0 ms.
Number of Words: The total number of words of BT data to be
exchanged. This includes all BTs in the queue.
Time per Word: At 57.6 Kbaud this time is 0.3 ms. At 115.2 Kbaud this
time is 0.2 ms.