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When writing the upper byte
CPU
[H'AA]
When writing the lower byte
CPU
[H'55]
Read Access: When the upper byte is read, the upper-byte data is sent directly to the CPU,
and the lower byte is loaded into TEMP. Next when the lower byte is read, the lower byte in
TEMP is sent to the CPU. Figure 9.17 shows a TCY read operation when H'AAFF is read
from TCY.
Bus
interface
Bus
interface
Figure 9.16 TLY Write Operation (CPU → TLY)
Module internal data bus
TEMP
[H'AA]
TLYH
[
]
Module internal data bus
TEMP
[H'AA]
TLYH
[H'AA]
TLYL
[
]
TLYL
[H'55]
201
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