Block Transfer Instructions; Rio Block Transfer General Functional Overview; Entering Parameters For Btr And Btw - Allen-Bradley SLC 500 Series Reference Manual
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Block Transfer Instructions
Publication 1747-RM001G-EN-P - November 2008
A BTR or BTW instruction writes information into its control structure
address (a three-word integer Control Block) when the instruction is entered.
The processor uses these values to execute the transfer.
You must enter an M1 file address into BTR Instructions and an M0 file
address into BTW Instructions. However, each instruction uses both the M0
and M1 file for that one hundred word buffer (1 through 32). For example, to
use the first available buffer (1) for a BTR, enter M1:e.100 into the "Buffer
File" field. However, M0:e.100 is also used by this BTR. So, the next BT
instruction must use another M-file buffer (2 through 32).
RIO Block Transfer General Functional Overview
The RIO scanner performs block transfers through control/status buffers
allocated in the scanner's M0 and M1 files. For BTW's, the data stored in the
Data File is copied into the M0 block transfer buffer, the M0 block transfer
buffer is then transferred to the RIO device. The corresponding M1 block
transfer buffer contains only BTW status information. For BTR's, the M0
block transfer buffer contains only BTR control information. The actual data
read from the remote device is received in the scanner's M1 block transfer
buffer. This data is then copied into the BTR Data File. A total of 32 block
transfer control/status buffers exist in the M0 (output/control) and the M1
(input/status) files.
Entering Parameters for BTR and BTW
The instructions have the following parameters.
• Data File - The address in the SLC processor's data file containing the
BTW or BTR data. Valid file types are B, N and F.
• BTR/BTW Buffer File - Block transfer buffer file address;
i.e. M0: e.x00, where "e" is the slot number of the scanner and "x" is the
buffer number. The range of the buffer number is from 1 to 32. Each
BTR and BTW instruction uses both the M1 and M0 files for a specific
buffer number. M0 is used for BTR control and for BTW data. M1 is
used for BTW status and BTR data.
Since buffer number 32 is utilized by the SLC
TIP
processor for Remote I/O passthru, you should not
assign buffer number 32 to a block transfer
instruction unless you do not intend to ever use
Remote I/O passthru.
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