5–20 RIO Block Transfer
Publication
17476.6 - July 1996
Below are points to consider when implementing BT operations:
• The minimum amount of scanner image that can be assigned to a
device on the RIO link is 1/4 logical rack in the G file
configuration. This allows up to four separate devices per logical
rack. Each device could have a maximum of four BTs configured
to it. Thus, up to 16 BTRs and/or 16 BTWs could be assigned to
each logical rack.
• If a BT device is a 1747-ASB RIO Adapter, then multiple SLC
500 modules (such as analog modules) could be scanned by the
1747-ASB and the data block transferred to the RIO scanner.
Since the RIO network handles one BT request per logical rack at
a time, there will be a delay before all devices in the 1747-ASB
rack can be accessed. Therefore you should only perform BTs as
necessary (i.e., “on demand”).
• Inhibiting a device on the RIO network (via control words
M0:e.8...11) precludes that device from block transfer operations.
Attempting to initiate a BT to an inhibited device results in an
error reply. The scanner will cancel a BT that is in progress if it
detects that the device is inhibited. Because of the asynchronous
nature of inhibiting a device that has a BT in progress, the BT
reply may indicate either a successful completion or an error. In
either case, the SLC control program must still clear the Enable
flag.
• All M0 and M1 BT buffers are cleared (set to all zeros) after a
power cycle and when the SLC processor goes from Program to
Run mode, Program to Test mode, or Test to Run mode.
When using complementary I/O, if you configure a complementary
device to use more I/O image space than an associated primary
device, then block transfers can only be performed to locations in the
complementary device that have associated I/O image space in the
primary device. For example, if a primary device is 1/2 logical rack
and a complementary device is a full logical rack, block transfers can
be performed only in the first 1/2 logical rack of the complementary
device. Attempting block transfers in the last half of the
complementary device will result in a BT error (error – 11 – device
not configured).
Word
7
Word 5
Word 6
Word 3
Word 4
Word 1
Word 2
Word 0
07815
0717 10Bit Number Octal
Logical
Rack 8
Complementary I/O Image
Primary I/O Image
Word
7
Word 5
Word 6
Word 3
Word 4
Word 1
Word 2
Word 0
Logical
Rack 0
Bit
Number Decimal
07815
0717 10Bit Number Octal
Bit Number Decimal
1/2 logical rack
configured and
usable
1/2 logical rack not
configured
1/2 logical rack
configured and usable
1/2 logical rack
configured, but not
usable for BT since
Words 4-7 are not
configured for the
primary device.
RIO Block Transfer
Application
Considerations
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