LC75808W(2010) View Datasheet(PDF) - SANYO -> Panasonic
Part Name
Description
Manufacturer
LC75808W Datasheet PDF : 38 Pages
| |||
LC75808W
Key Scan Operation Functions
1. Key scan timing
The key scan period is 384T(s). To reliably determine the on/off state of the keys, the LC75808W scans the keys
twice and determines that a key has been pressed when the key data agrees. It outputs a key data read request (a low
level on DO) 800T(s) after starting a key scan. If the key data dose not agree and a key was pressed at that point, it
scans the keys again. Thus the LC75808W cannot detect a key press shorter than 800T(s).
KS1
*3 1
1
*3
KS2
*3
2
2
*3
KS3
*3
KS4
*3
3
4
3
4
*3
T=
1
fosc
*3
KS5
*3
5
5
*3
KS6
*3
6
6 *3
Key on
768T [s]
A12911
Note: *3. Note that the high/low states of these pins are determined by the KC1 to KC6 bits in the control data, and
that key scan output signals are not output from pins that are set to low.
2. In normal mode
• The pins KS1 to KS6 are set to high or low by the KC1 to KC6 bits in the control data.
• If a key on one of the lines corresponding to a KS1 to KS6 pin which is set high is pressed, a key scan is started
and the keys are scanned until all keys are released. Multiple key presses are recognized by determining whether
multiple key data bits are set.
•
If
a
key
is
pressed
for
longer
than
800T(s)
(Where
T=
1
fOSC
)
the
LC75808W
outputs
a
key
data
read
request
(a
low
level on DO) to the controller. The controller acknowledges this request and reads the key data. However, if CE is
high during a serial data transfer, DO will be set high.
• After the controller reads the key data, the key data read request is cleared (DO is set high) and the LC75808W
performs another key scan. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1kΩ
and 10kΩ).
Key input 1
Key input 2
Key scan
CE
DI
800T [s ]
800T [s]
800T [s ]
Serial data
transfer
Serial data
transfer
Key address(43H)
Serial data
transfer
Key address
Key address
DO
Key data read request
Key data read
Key data read
Key data read
Key data read request
Key data read request
T=
1
fosc
A12912
No.6370-22/38
Share Link: 