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CHAPTER 3 INTERRUPTS
■ I/O Register Address Pointer (IOA)
This is a 16-bit register that indicates the low-order address (A15 to A00) of the buffer and I/O register
used for data transfer. The high-order address (A23 to A16) are all zeroes, and any I/O between addresses
"000000
configuration.
bit
15
14
13
12
A15 A14 A13 A12 A11 A10 A09 A08 A07 A06 A05 A04 A03 A02 A01 A00
■ Buffer Address Pointer (BAP)
This 24-bit register holds the address used for the next EI
Therefore, each EI
of ISCS is set to "0" (update enabled), only the low-order 16 bits of BAP changes and BAPH does not
change.
74
" and "00FFFF
" can be specified. Figure 3.7-4 shows the I/O register address pointer
H
H
Figure 3.7-4 I/O Register Address Pointer Configuration
11
10
9
8
7
2
OS channel can be used for transfer with anywhere in the 16-Mbyte space. If the BF bit
6
5
4
3
2
2
OS transfer. BAP exists for each EI
1
0
IOA
(Undefined when reset)
2
OS channel.
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