HD64F2149 Datasheet, PDF (576/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

Start
Set KBIOE bit
[1]
Read KBCRH
[2]
KCLKI
No
and KDI bits both
1?
Yes
2
Set I/O inhibit (KCLKO = 0) KDO remains at 1
KBE = 0
[3]
(KBBR reception disabled)
Wait
Set start bit (KDO = 0)
Set I/O inhibit (KCLKO = 1)
[4]
KCLKO remains at 0
[5]
KDO remains at 0
i=0
Read KBCRH
KCLKI = 0?
Yes
Set transmit data
(KDO = D(i))
[6]
No
[1] Set the KBE bit to 1 in KBCRH, and the
KBIOE bit to 1 in KBCRL.
[2] Read KBCRH, and if the KCLKI and
KDI bits are both 1, write 0 in the
KCLKO bit (set I/O inhibit).
[3] Write 0 in the KBE bit (disable KBBR
receive operation).
[4] Write 0 in the KDO bit (set start bit).
[5] Write 1 in the KCLKO bit (clear I/O
inhibit).
[6] Read KBCRH, and when KCLKI = 0,
set the transmit data in the KDO bit
(LSB-first). Next, set the parity bit and
stop bit in the KDO bit.
[7] After transmitting the stop bit, read
KBCRL and confirm that KDI = 0
(receive completed notification from the
keyboard).
[8] Read KBCRH. Confirm that the KCLKI
and KDI bits are both 1.
The transmit operation can be continued
by repeating steps [2] to [8].
Read KBCRH
KCLKI = 1?
No
Yes
i=i+1
i > 9?
No
Yes
Read KBCRH
No
KCLKI = 1?
Yes
1
i = 0 to 7: Transmit data
i = 8: Parity bit
i = 9: Stop bit
Figure 17.5 Sample Transmit Processing Flowchart
542