Rockwell Automation 6008-SV2R VMEbus remote I/O Scanner - Manual (Page 55)

Chapter
Operating in SVĆCompatible Mode
5
5Ć4
Table 5.A
Descriptions of the global memory areas
This area: stores the:
input and output image tables input and output data for as many as 8 logical I/O racks with no more than 16 adapters.
control/status area
operating status byte reflects the current status of the scanner (Figure 5.2)
lets the VME master processor poll the scanner's status without interrupting
ongoing operations
confirmation status
byte
contains the result of the executed command
A result of 00 (hex) indicates the command completed successfully. See chapter 9
for a list of error codes.
command byte identifies the command the VME master processor wants the scanner to
execute next
address byte contains I/O rack, group, and slot parameters for block transfer commands
For more information, see BT READ command on page 5Ć25 or BT WRITE
command on page 5Ć27.
blockĆtransfer tag byte provided by the VME master processor to uniquely identify each
blockĆtransfer request
semaphore byte provides for the integrity of command requests, command responses, and completed
block transfers
If bit 7 is set, a VME master processor is using the control/status and general data
area or the scanner just completed a blockĆtransfer and set the semaphore so no
other VME master processor will overwrite the data. If the semaphore is set because
of a blockĆtransfer, the appropriate VME master will know to come and retrieve the
data and reset the semaphore. If the semaphore bit is clear, the general data area is
available for access by any VME master processor.
Important: A VME master processor doesn't use the semaphore when it accesses
the I/O image table. The VME master processor can access the I/O image
table anytime.
For command requests, the scanner returns status, either confirmation or error, when
the command is complete. When the VME master processor receives the
confirmation status, it must retrieve the data from the general data area and clear
the semaphore.
Important: Only 1 command can be issued at a time. A status confirmation or error
must be received before a new command is issued.
length of data byte specifies the amount of data associated with a command or response
Only the lower byte is used. Interpret the length of data based on the context of the
requested command or received confirmation (i.e., number of words for
blockĆtransfers and bytes for scanner management requests).
general data area contains input parameters and result data for scanner commands
scanner interrupt and VME ID interrupt from the VME master processor to the scanner
The scanner interrupt area and VME ID area can be read anytime without causing an interrupt to the scanner.
It contains 32 words in which the odd (lower byte) only is used; the information is an ASCII character string:
V.M.E.I.D.A.-.B.6.0.0.8.-.S.V.2.R. .x. .y. or V.M.E.I.D.A.-.B.6.0.0.8.-.S.V.1.R. .x. .y.
where .x. .y. are the series and revision levels of the scanner. For example:
V.M.E.I.D.A.-.B.6.0.0.8.-.S.V.2.R. .A. .A. for series A, revision A.
Writing to any byte in this area interrupts the scanner. The scanner then looks at the command byte to
determine which command to execute.
All even bytes have the value 0xFF; all odd bytes without ASCII characters have the value 0x00.