HD66724 Datasheet, PDF (61/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
The key scan data can be read by an MPU via a serial interface. First, a start byte should be transferred.
After the HD66724/HD66725 have received the start byte, the MPU reads scan data KSD7 to KSD0 from
the SCAN0 register starting from the MSB. Similarly, the MPU reads the data from SCAN1, SCAN2 and
SCAN3 in that order. After reading SCAN3, the MPU starts reading at SCAN0 again.
The HD66724/HD66725 may be read out while they are latching scan data and are thus unstable.
Consequently, they should also be reconfirmed with software if required.
Write a dummy instruction ("00H") before reading the key scan data.
a) Scan Data Read Timing through Clock-synchronized Serial Bus Interface
Transfer start
CS*
(Input)
Transfer end
SCL
(Input)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
SDA
(Input/
output)
0 1 1 1 0 ID 0 1 KSD7 KSD6 KSD5 KSD4 KSD3 KSD2 KSD1 KSD0
Device ID code
RS R/W
Start byte
SCAN0 data transmission
b) Consecutive Scan Data Read Timing
SCL
(Input)
SDA
(Input/
output)
Start
byte
Wait
Wait
Wait
Wait
SCAN0
data
SCAN1
data
SCAN2
data
SCAN3
data
SCAN0
data
Figure 29 Scan Data Serial Transfer Timing
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