User`s manual
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5
[2] BD.REQ signal
The following explains operation of the BD.REQ signal which is handy when used for reading/
writing of block data.
Normally, the BD.REQ signal is ON when block data transfer is possible. The BD.REQ signal turns
OFF during transfer when the block data read/write relays turn ON. The following shows the timing
of data transfer using the BD.REQ signal.
PS internal transfer
calculation
PC
I/O
refreshing
PC side
data
Write
relay
Write
address
EX EX
EX
Final check calculation
PS internal BD.REQ
PC side BD.REQ
Block 0 data Block 1 data Block 2 data Block 3 data
01 2 3
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
Write timing
PS internal transfer
calculation
PC
I/O
refreshing
PC side
data
Read
relay
Read relay
PC→PS
EX EX
EX
EX EX
PS internal BD.REQ
PC side BD.REQ
Block 0 data Block 1 data Block 2 data Block 3 data
Block 4 data
01 2 3 4
BD.REQ signal
turns ON after
I/O refreshing
at transfer.
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
Read timing
When the read relay is ON at I/O refreshing on the 1st scan, the BD.REQ signal is turned OFF, and
calculation for data transfer is started.
The block data is transferred at I/O refreshing on the 2nd scan. After this I/O refreshing ends, the
BD.REQ signal is turned ON.