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Chapter 14 Automatic Transfer Controller
Operation
XIV - 12
14-3-3 Setting the Data Transfer Count
Transfer data counter (AT1TRC) function
You can preset the data transfer count is preset for ATC1. Set the value in the ATC1 transfer counter
(AT1TRC). The counter decrements by one each time ATC1 transfers one byte of data.
The value in the transfer data counter is indeterminate upon reset. The program must initialize the
counter before activating ATC1. Note that ATC1 cannot be activated if the transfer data counter is set to
x'00'.
Data transfer operations using the transfer data counter (AT1TRC)
There are two main types of ATC1 data transfers, standard and burst transfers. (See section 14-3-4
" Setting the Data Transfer Modes"). The transfer counter operates differently depending on the transfer
type.
1. Standard transfers [transfer modes 0 to D]
In standard transfers, the transfer counter decrements every time ATC1 is activated. When the counter
reaches x'00' after a data transfer, ATC1 generates an interrupt (ATC1IRQ). This means that for stan-
dard transfers, the program must set the counter to the number of times ATC1 needs to be activated.
2. Burst transfers [transfer modes E to F]
In burst transfers, ATC1 is activated once and continuously transfers multiple bytes of data. In this case,
the program must set the counter to the number of data bytes contained in the burst transfer. When the
burst transfer starts, the transfer counter decrements every time one byte of data is transferred. When
the counter reaches x'00', ATC1 generates an interrupt (ATC1IRQ).
It is also possible to force ATC1 to shut down during a burst transfer using external interrupt 0.
(See 14-3-4 "Setting the Data Transfer Modes").
The transfer data counter (AT1TRC)
The transfer data counter can be set to a maximum 255 transfers (for standard transfers) or 255 bytes
(for burst transfers). Note that setting the counter to x'00' disables transfers.