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Chapter 14 Automatic Transfer Controller
Operation
XIV - 18
14-3-9 Transfer Mode 4
In transfer mode 4, ATC1 automatically transfers two bytes (one word) of data from any memory space to
the I/O space (special registers : x'03F00' - x'03FFF') every time an ATC1 activation request occurs.
(1)
(2)
(3)
(2)
(4)
AT1MAP0
AT1MAP0 + 1
AT1MAP0 + 2
AT1MAP0 + 3
AT1MAP1 (odd)
Memory Pointer 0
00000 - 3FFFF 03F00 - 03FFF
Memory Pointer 1
(Only lower
8 bits are valid)
AT1MAP1 (even)
Always set an even address as the destination I/O address in memory pointer 1. When ATC1
transfers one word to the I/O space, ATC1 can transfer the even address set in memory
pointer 1 and the odd address that immediately follows it.
In transfer mode 4, ATC1 executes a data byte transfer twice, to send one data word, each time it is
activated. The value in memory pointer 0 increments by one each time a byte-length data transfer ends.
As a result, the source address for the next ATC1 operation is two addresses higher than that for the
previous operation.
In this word-length transfer, ATC1 transfers the first data byte to an even address in the I/O space and
the second data byte to an odd address in the I/O space.
Set the data transfer data count for ATC1 in the transfer data counter (AT1TRC). The counter can be set
to a maximum of 255 transfers. The counter decrements each time ATC1 is activated (after each word
transfer). When it reaches x'00', an interrupt (ATC1IRQ) occurs and the automatic transfer ends.
Figure 14-3-6 Transfer Mode 4
Set the source address in 18-bit memory pointer 0 (AT1MAP0H, M, L), and set the destination I/O
address in the lower 8 bits of memory pointer 1(AT1MAP1L). The upper 10 bits of the I/O space address
(x'03F') need not to be set in AT1MAP1H and AT1MAP1M.