Rockwell Automation 6008-SV2R VMEbus remote I/O Scanner - Manual (Page 85)

Chapter
Operating in SVĆSuperset Mode
6
6Ć4
Table 6.A
Descriptions of the global memory areas
This area: stores the:
input and output image table
input and output data for as many as 16 logical I/O racks with no more than 32 adapters.
control/status area operating status byte reflects the current status of the scanner
lets the VME master processor poll the scanner's status without interrupting
ongoing operations
see Figure 6.2 on page 6Ć5
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 6Ć28
BT WRITE command on page 6Ć32
CONTINUOUS BT READ command on page 6Ć36
CONTINUOUS BT WRITE command on page 6Ć40
block transfer tag byte provided by the VME master processor to uniquely identify each oneĆshot block
transfer request or continuous blockĆtransfer entry
block transfer interrupt
byte
indicates the VME interrupt level and interrupt acknowledgement vector for when a
continuous block transfer periodically completes
For more information, see BT WRITE command on page 6Ć32 or BT READ
command on page 6Ć36. Use the SETUP command to specify the interrupt level and
interrupt vector.
input image table
monitor index word
when the input image table monitor is enabled, this word contains the index of the
last entry that changed in the input image table
when the input image table monitor is disabled, this word is undefined
Use the SETUP command to enable or disable the input image table monitor.
semaphore byte provides for the integrity of command requests, command responses, and completed
oneĆshot 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 block transfer and set the semaphore so no
other VME master processor will overwrite the data. If the semaphore is set because
of a block transfer, 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.