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CHAPTER 4 DMA
4.3.2
I/O Register Address Pointer (IOA)
This section describes the I/O Register Address Pointer (IOA).
■ I/O Register Address Pointer (IOA)
The I/O Register Address Pointer (IOA) is a 16-bit register and indicates the lower addresses (A15 to A0) of
the I/O register. Its upper addresses (A23 to A16) are all "0", allowing any I/O address space in the range
from "000000
When "Update Performed" is specified with the DMACS:IF bit of the DMA Control Register, IOA is
incremented by 1 at byte transfer; and incremented by 2 at word transfer. When "Update Not Performed" is
specified with the DMACS:IF bit, IOA is fixed (IOA does not change).
Figure 4.3-3 "I/O Register Address Pointer (IOA) Configuration" shows the configuration of the I/O Register
Address Pointer (IOA).
Figure 4.3-3 I/O Register Address Pointer (IOA) Configuration
Address:
15
14
8*ch +
0x105, 0x104
A15
A14
Read/Write:
(R/W)
(R/W) (R/W) (R/W) (R/W) (R/W) (R/W) (R/W)
Initial Value:
X
X
R/W: readable and writable
128
" to "00FFFF
" to be specified.
H
H
IOAH
13
12
11
10
09
A13
A12
A11
A10
A9
X
X
X
X
X
MB96300 Super Series Hardware Manual
IOAL
08
07
06
05
04
A8
A7
A6
A5
A4
(R/W)
(R/W) (R/W) (R/W) (R/W) (R/W)
X
X
X
X
X
03
02
01
00
Bit No.
A3
A2
A1
A0
IOA
(R/W) (R/W)
X
X
X
X
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