User guide

Software
890 USE 108 00 August 2001 63
LOAD
Instruction Block
(E984-258/265/
275/285 Only)
The LOAD block loads a block of 4x registers (previously saved) from state RAM
where they are protected from unauthorized modification.
The size is three nodes high
The PLC compatibility is PC-E984-258, PC-E984-265, PC-E984-275, and PC-
E984-285.
The opcode is 55 hex
The following figure shows the block structure of the LOAD block.
Inputs
LOAD has one control input that starts the operation and it should remain ON until
the operation has completed successfully or an error has occurred.
Outputs
LOAD may produce three possible outputs. The outputs from the top node goes
ON while a LOAD operation is in progress. The output from the middle node goes
ON when a LOAD is requested from a buffer where no data has been saved.
Therefore, no LOAD is allowed. This prevents inadvertent overwriting of data in
state RAM. The output from the bottom node goes ON when a LOAD request is
not equal to the registers that were saved.
Top Node Content
The top node specifies a block of 4x registers to be loaded from state RAM. The
4x register entered here defines the beginning register of the block.
Middle Node Content
The middle node defines the specific buffer where the block of data is to be
loaded. Four 512 word buffers are allowed. Each buffer is defines by placing its
corresponding value in the middle node, that is, the value 1 represents the first
buffer, value 2 represents the second buffer and so on. The legal values are 1, 2,
3, and 4. When the PLC is started all four buffers are zeroed. Therefore, you may
not LOAD data from the same buffer without first saving it. When this is attempted
the middle output goes ON. In other words, once a buffer is used, it may not be
used again until the data has been removed.
Bottom Node Content
The bottom node contains the number of words to be loaded. The range is 1...
512.
Start LOAD
operation
LOAD is active
Nothing SAVED
4xxxx
1, 2, 3, 4
LOAD
#0512
Length not equal to SAVED length