HD64F2168 Datasheet, PDF (163/874 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

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.
φ
Address bus
IOS
Bus cycle
T₁
T₂
T₃
External addresses selected by IOS
Figure 6.2 IOS Signal Output Timing
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 6.15.
Table 6.15 Address Range for IOS Signal Output
IOS1
0
1
IOS0
0
1
0
1
IOS Signal Output Range
H'FFF000 to H'FFF03F
H'FFF000 to H'FFF0FF
H'FFF000 to H'FFF3FF
H'FFF000 to H'FFF7FF
(Initial value)
Rev. 3.00, 03/04, page 123 of 830