HD64F2149YV datasheet(596/1075 Pages) RENESAS

596 / 1075 page

Section 17 Keyboard Buffer Controller

Rev. 3.00 Jan 18, 2006 page 568 of 1044

REJ09B0280-0300

Start

Set KBIOE bit

Read KBCRH

KCLKI

and KDI bits both

Set KBE bit

Receive enabled state

KBF = 1?

PER = 0?

KBS = 1?

Read KBBR

Receive data processing

Clear KBF flag

(receive enabled state)

Keyboard side in data

transmission state.

Execute receive abort

processing.

Error handling

[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,

the system automatically

drives KCLK high, setting

the receive enabled state.

The receive operation can be

continued by repeating steps

[3] to [6].

[1]

[2]

[3]

[4]

[5]

[6]

Yes

Figure 17.3 Sample Receive Processing Flowchart

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