Figure 17.3 Sample Receive Processing Flowchart - Renesas H8S Series Hardware Manual

Section 17 Keyboard Buffer Control Unit (KBU)
Start
Set KBIOE bit
Read KBCRH
KCLKI
and KDI bits both
1?
Set KBE bit
Receive enabled state
KBF = 1?
PER = 0?
KBS = 1?
Read KBBR
Receive data processing
Clear KBF flag
(receive enabled state)
Rev. 3.00 Jul. 14, 2005 Page 594 of 986
REJ09B0098-0300
[1]
[2]
No
Yes
Keyboard side in data
transmission state.
[3]
Execute receive abort
processing.
No
[4]
Yes
No
Yes
No
Yes
Error handling
[6]

Figure 17.3 Sample Receive Processing Flowchart

[1] Set the KBIOE bit to 1 in
KBCRL.
[2] Read KBCRH, and if the
KCLKI and KDI bits are
both 1, set the KBE bit
(receive enabled state).
[3] Detect the start bit output
on the keyboard side and
receive data in
synchronization with the fall
of KCLK.
[4] When a stop bit is received,
the keyboard buffer
controller drives KCLK low
to disable keyboard
transmission (automatic I/O
inhibit).
If the KBIE bit is set to 1 in
KBCRH, an interrupt
request is sent to the CPU
at the same time.
[5] Perform receive data
processing.
[6] Clear the KBF flag to 0 in
KBCRL. At the same time,
[5]
the system automatically
drives KCLK high, setting
the receive enabled state.
The receive operation can be
continued by repeating steps
[3] to [6].