HD64F2149YV datasheet(598/1075 Pages) RENESAS

598 / 1075 page

Section 17 Keyboard Buffer Controller

Rev. 3.00 Jan 18, 2006 page 570 of 1044

REJ09B0280-0300

Start

Set KBIOE bit

KCLKI = 0?

Read KBCRH

KCLKI

and KDI bits both

Set I/O inhibit (KCLKO = 0)

KBE = 0

(KBBR reception disabled)

KDO remains at 1

Wait

Set start bit (KDO = 0)

Set I/O inhibit (KCLKO = 1)

KCLKO remains at 0

KDO remains at 0

i = 0

Read KBCRH

Set transmit data

(KDO = D(i))

Read KBCRH

KCLKI = 1?

i = i + 1

> 9?

Read KBCRH

KCLKI = 1?

Yes

i = 0 to 7: Transmit data

i = 8: Parity bit

i = 9: Stop bit

Yes

[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].

[1]

[2]

[3]

[4]

[5]

[6]

Figure 17.5 Sample Transmit Processing Flowchart

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