205
2.
Read access
In access to TCF, when the upper byte is read the upper-byte data is transferred directly to the CPU
and the lower-byte data is transferred to TEMP. Next, when the lower byte is read, the lower-byte
data in TEMP is transferred to the CPU.
In access to OCRF, when the upper byte is read the upper-byte data is transferred directly to the
CPU. When the lower byte is read, the lower-byte data is transferred directly to the CPU.
Figure 9-5 shows an example in which TCF is read when it contains H'AAFF.
Figure 9-5 Read Access to TCF (TCF
→
CPU)
Read upper byte
CPU
(H'AA)
TEMP
(H'FF)
TCFH
(H'AA)
TCFL
(H'FF)
Bus
interface
Module data bus
Read lower byte
CPU
(H'FF)
TEMP
(H'FF)
TCFH
(AB)*
TCFL
(00)*
Bus
interface
Module data bus
Note:
*
H'AB00 if counter has been updated once.