8.2.2 I/O Address Registers (IOAR)
An I/O address register (IOAR) is an 8-bit readable/writable register that specifies a source or
destination address. The IOAR value is the lower 8 bits of the address. The upper 16 address bits
are all 1 (H'FFFF).
An IOAR functions as a source or destination address register depending on how the DMAC is
activated: as a source address register if activation is by a receive-data-full interrupt from the SCI
(channel 0), and as a destination address register otherwise.
The IOAR value is held fixed. It is not incremented or decremented when a transfer is executed.
The IOARs are not initialized by a reset or in standby mode.
8.2.3 Execute Transfer Count Registers (ETCR)
An execute transfer count register (ETCR) is a 16-bit readable/writable register that specifies the
number of transfers to be executed. These registers function in one way in I/O mode and idle
mode, and another way in repeat mode.
•
I/O mode and idle mode
In I/O mode and idle mode, ETCR functions as a 16-bit counter. The count is decremented by
1 each time one transfer is executed. The transfer ends when the count reaches H'0000.
Bit
Initial value
Read/Write
7
R/W
6
R/W
5
R/W
4
R/W
3
R/W
0
R/W
2
R/W
1
R/W
Source or destination address
Undetermined
Bit
Initial value
Read/Write
14
R/W
12
R/W
10
R/W
8
R/W
6
R/W
0
R/W
4
R/W
2
R/W
Transfer counter
Undetermined
15
R/W
13
R/W
11
R/W
9
R/W
7
R/W
1
R/W
5
R/W
3
R/W
191
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