201
Bus
interface
CPU
[H'AA]
TEMP
[H'AA]
TLYH
[ ]
TLYL
[ ]
Module internal data bus
When writing the upper byte
CPU
[H'55]
TEMP
[H'AA]
TLYH
[H'AA]
TLYL
[H'55]
Module internal data bus
When writing the lower byte
Bus
interface
Figure 9.16 TLY Write Operation (CPU
→
TLY)
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.