bu9768ak ROHM Co. Ltd., bu9768ak Datasheet - Page 13

• Manufacturer Part Number: bu9768ak
• Description: Driver Segmented Module With Input Function
• Manufacturer: ROHM Co. Ltd.

(2) Key scan operation
With the BU9768AK / BU9768AKV, up to 30 key inputs can be received.
One key scan requires 15ms (if f
received. Also, in order to prevent chattering, the key scan waveform (KO output) reaches the HIGH level twice dur-
ing one key scan. After scanning has been carried out twice, the data from the two scans is compared, and if the
data for all of the keys does not match, an error occurs.
With the BU9768AK / BU9768AKV, if normal key input is received, DO changes from HIGH to LOW, so if DO is con-
nected to the interrupt input pin of the controller, interrupt processing can be carried out based on the key input. Also,
after DO changes to LOW following completion of a key scan, a new key scan cannot be carried out until all of the
key data has been read.
If multiple keys are pressed at once, multiple key data is set for the various key inputs to be distinguished.
1) Key scans and key data communications
Standard ICs
KO
KO
KO
KO
KO
KO
DO
1
2
3
4
5
6
KEY ON
Key data
reading
Key scan
Fig. 10 Relationship between key scan and data communications
Key1
Key2
Key3
DO
OSC
= 38kHz, 582 / f
Key scan
Fig. 9 Key scan operation
15ms
OSC
(sec)). Key scans which are shorter than this time cannot be
Key scan
New key scan cannot be carried out
until all data has been read.
Data corresponding to one key scan
BU9768AK / BU9768AKV
When the key scan is completed
without problems, DO changes
from HIGH to LOW.
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