Detailed Operation Of Rio Block Transfer - Allen-Bradley 1747-SN User Manual

Detailed Operation of RIO
Block Transfer
You use the 1747-SN Scanner M0 file BTR/BTW output control
buffers to set up and control BT operations. Status information
regarding the progress and completion of BTR/BTW operations
displays in corresponding M1 file input status buffers.
This section describes step-by-step how the RIO scanner uses
M0/M1 files to accomplish block transfer operations. The steps
below are based on the following assumptions:
The size of the M0 and M1 files has already been set to 3,300
words. (You set the M file sizes in APS while in off-line
programming mode.)
No pending BT operation utilizing a particular M0 output/control
and M1 status/control buffer is in progress.
Both the M0/M1 control/status buffers are completely empty.
Important:
Timing diagrams describing BT control and status flag
operation follow this section.
1. You set up a BTR or BTW by filling in control information
(about block transfer length, logical rack, logical group, and
logical slot address) in an M0 output/control buffer. If you want
to set up a BTW, then you must place your write data in the BTW
data area of the M0 output control buffer. You set up M0 buffer
information in an integer file and a COP instruction copies the
information into the M0 output control file.
2. Your SLC control program initiates a BTR/BTW operation by
filling in the BT control field (M0:e.100/7) of the M0 BT buffer.
This indicates whether a BTR or BTW will be initiated (0 = BTW
and 1 = BTR).
Your SLC control program also sets the EN (Enable) flag
(M0:e.100/15) which signals the RIO scanner that a new block
transfer operation is to begin.
3. The scanner processes the BTR/BTW when it detects that the
SLC control program has set the EN flag.
If the RIO scanner detects any problem at this point (such as
invalid BT control field, or unconfigured device) the M1 input
status buffer's error code field fills in and the ER (Error) flag in
the status field sets. If no problems occur, the EW (Enable
Waiting) flag and ST (Start) flag set in the status field. (Note that
the ST flag will not set if the scanner is already in the process of
block transferring data to a location within the same logical rack.
The ST flag will set only after any previous pending BTs to the
same logical rack have been completed and the BT request has
been scheduled on the RIO link.)
RIO Block Transfer
Publication 1747 6.6 - July 1996
5–13