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Section 6 Bus Controller (BSC)
6.4.3
I/O Select Signals
The LSI can output I/O select signals (IOS); the signal is driven low when the corresponding
external address space is accessed. Figure 6.2 shows an example of IOS signal output timing.
Address bus
Enabling or disabling IOS signal output is performed by the IOSE bit in SYSCR. In the extended
mode, the IOS pin functions as an AS pin by a reset. To use this pin as an IOS pin, set the IOSE
bit to 1. For details, see section 8, I/O Ports.
The address ranges of the IOS signal output can be specified by the IOS1 and IOS0 bits in BCR,
as shown in table 6.12.
Table 6.12 Address Range for IOS Signal Output
IOS1
IOS0
0
0
1
1
0
1
Rev. 1.00 Mar. 12, 2008 Page 124 of 1178
REJ09B0403-0100
T
1
φ
IOS
Figure 6.2 IOS Signal Output Timing
IOS Signal Output Range
H'FFF000 to H'FFF03F
H'FFF000 to H'FFF0FF
H'FFF000 to H'FFF3FF
H'FFF000 to H'FFF7FF
Bus cycle
T
2
External addresses selected by IOS
T
3
(Initial value)
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