523
Chapter 31 External Bus
2.External Bus Interface Registers
[Bits 7,6] W07-06 (Read -> Write Idle Cycle)
The read -> write idle cycle is set to prevent collision of read data and write data on the data bus when a write
cycle follows a read cycle. During an idle cycle, all chip select signals are negated and the data terminals
maintain the high impedance state. If a write cycle follows a read cycle or an access operation to another chip
select area occurs after a read cycle, the specified idle cycle is inserted. Table 2-7 "Settings of the Idle Cycle"
lists the settings for idle cycles.
[Bits 5, 4] W05, W04 (Write Recovery Cycle)
The write recovery cycle is set if a device that limits the access period after write access is to be controlled.
During a write recovery cycle, all chip select signals are negated and the data pins maintain the high
impedance state. If the write recovery cycle is set to 1 or more, a write recovery cycle is always inserted after
write access.
Table 2-8 "Settings for the Number of Write Recovery Cycles" lists the settings for the number of write
recovery cycles.
Table 2-7 Settings of the Idle Cycle
W07 W06 Read -> write idle cycles
0 0 0 cycle
0 1 1 cycle
1 0 2 cycles
1 1 3 cycles
Table 2-8 Settings for the Number of Write Recovery Cycles
W05 W04 Write recovery cycles
0 0 0 cycle
0 1 1 cycle
1 0 2 cycles
1 1 3 cycles
