
[AK4673]
MS0670-E-00
2007/09
- 77 -
■
WRITE Operation Sequence
The selection of channel input of the AK4673 is determined by a command byte. When accelerate command (A2= “0”) is
sent, the switch on timing of the driver switch is 18
th
falling edge of SCL regardless of PD0 bit. The accelerate command
is to accelerate the timing of desired driver SW ON to ensure that AK4673 needs more settling time. Actually sampling
timing is on the time of READ operation, it is possible to take settling time longer even when the impedance of the touch
screen is large.
AK4673
ACK
0
Touch Driver SW
AK4673
ACK
S
X1
A2=0, PD0=0 or 1
A2=1, PD0=1
A2=1, PD0=0
A2
PD0
STOP
MODE
A1
A0
X2
CAD0
0
19
I
II
III
IV
Command Byte
SCL
SDA
START
1 0 0
0 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1 0 0
R/ W
Address Byte
Figure 74 write operation and Driver SW timing
■
READ Operation Sequence
A/D conversion is synchronized with SCL. Sampling time is the one SCL clock period (SCL7
↓~
SCL8
↓
) on the end of
writing address byte and then hold. A/D conversion is held on the next 12 SCL period (except MASTER ACK). After
address byte is sent, the readout sequence starts with an acknowledge, which is the responce of the AK4673 when the
address maches. The MSB data byte will follow (D11
~
D4) then issued acknowledge by master. The LSB data byte
(D3
~
D0, followed four “0”) will be followed by NOT acknowledge bit (NACK) from master in order to terminate the
read transfer. The master will then issued STOP that ends read operation or Repeated Start condition that keeps write or
read operation. The master will issue Repeated Start Condition or START condition followed by read operation again.
AK4673 repeats A/D data updated [continuous read operation]. Master must issue STOP condition after terminating the
last read out of A/D data.
Address Byte
Data Byte (MSB)
Data Byte (LSB)
MASTER
ACK
MASTER
NACK
0
“H”
A2=“0” or A2=“1” , PD0=“1”
A2=“1”, PD0=“0”
Sampling
AD conversion
0
A2=“0”, PD0=“0”
28
V
VI
SCL
SDA
START
1 0 0
1 0
CAD0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1 0 0
AK4673
ACK
D11
D10
D9
D8
D7
D6
D4
D5
R/ W
19
20
21
22
23
24
25
26
27
D3
D2
D1
D0
0
0
0
1
0
Touch Driver SW
Repeated START
IV
Figure 75 Read data Sequence