AD7879 Analog Devices, AD7879 Datasheet - Page 33

• Manufacturer Part Number: AD7879
• Description: Low Voltage Controller for Touch Screens
• Manufacturer: Analog Devices

Specifications of AD7879

• Resolution (bits): 12bit
• # Chan: 6
• Sample Rate: 105kSPS
• Interface: I²C/Ser 2-Wire,Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni Vdd
• Adc Architecture: SAR
• Pkg Type: CSP,WLCSP

SCL
Reading Data
A read transaction begins when the master writes the command
word to the AD7879/AD7889 with the read/write bit set to 1. The
master then supplies 16 clock pulses per data-word to be read,
and the AD7879/AD7889 clock out data from the addressed
register on the DOUT line. The first data-word is clocked out
on the first falling edge of SCL following the command word,
as shown in Figure 41.
DIN
CS
NOTES
1. MULTIPLE SEQUENTIAL REGISTERS CAN BE LOADED CONTINUOUSLY.
2. THE FIRST (LOWEST ADDRESS) REGISTER ADDRESS IS WRITTEN, FOLLOWED BY MULTIPLE 16-BIT DATA-WORDS.
3. THE ADDRESS AUTOMATICALLY INCREMENTS WITH EACH 16-BIT DATA-WORD (ALL 16 BITS MUST BE WRITTEN).
4. CS IS HELD LOW UNTIL THE LAST DESIRED REGISTER HAS BEEN LOADED.
5. 16-BIT COMMAND WORD SETTINGS FOR SEQUENTIAL WRITE OPERATION:
CW
CW[15:11] = 11100 (ENABLE WORD)
CW[10] = 0 (R/W)
CW[9:0] = [AD9, AD8, AD7, AD6, AD5, AD4, AD3, AD2, AD1, AD0] (STARTING MSB JUSTIFIED REGISTER ADDRESS)
15
DOUT
1
SCL
DIN
CS
ENABLE WORD
CW
14
2
CW
13
NOTES
1. DATA BITS ARE LATCHED ON SCL RISING EDGES. SCL CAN IDLE HIGH OR LOW BETWEEN WRITE OPERATIONS.
2. THE 16-BIT COMMAND WORD MUST BE WRITTEN ON DIN: 5 BITS FOR ENABLE WORD, 1 BIT FOR R/W, AND 10 BITS FOR REGISTER ADDRESS.
3. THE REGISTER DATA IS READ BACK ON THE DOUT PIN.
4. X DENOTES DON’T CARE.
5. XXX DENOTES HIGH IMPEDANCE THREE-STATE OUTPUT.
6. CS IS HELD LOW UNTIL ALL REGISTER BITS HAVE BEEN READ BACK.
7. 16-BIT COMMAND WORD SETTINGS FOR SINGLE READBACK OPERATION:
3
CW[15:11] = 11100 (ENABLE WORD)
CW[10] = 1 (R/W)
CW[9:0] = [AD9, AD8, AD7, AD6, AD5, AD4, AD3, AD2, AD1, AD0] (10-BIT MSB JUSTIFIED REGISTER ADDRESS)
CW
XXX
15
t
CW
2
12
1
t
1
4
ENABLE WORD
XXX
CW
14
CW
11
2
5
t
3
XXX
CW
13
R/W
CW
10
3
16-BIT COMMAND WORD
6
XXX
CW
12
CW
4
9
7
XXX
CW
11
CW
5
8
8
R/W
CW
XXX
t
10
4
STARTING REGISTER ADDRESS
CW
6
7
16-BIT COMMAND WORD
9
XXX
CW
9
CW
7
6
10
XXX
CW
Figure 40. Sequential Register Write, SPI Timing
Figure 41. Single Register Readback, SPI Timing
8
CW
8
5
11
CW
XXX
7
t
CW
5
9
4
12
REGISTER ADDRESS
XXX
CW
6
10
CW
3
Rev. C | Page 33 of 40
13
XXX
CW
5
11
CW
2
14
CW
XXX
4
12
CW
1
15
CW
XXX
3
13
CW
0
16
The AD7879/AD7889 continue to clock out data on the DOUT
line provided that the master continues to supply the clock signal
on SCL. The read transaction ends when the master takes CS high.
If the AD7879/AD7889 address pointer reaches its maximum
value, the AD7879/AD7889 repeatedly clock out data from the
addressed register. The address pointer does not wrap.
XXX
CW
2
14
D15
17
XXX
CW
1
15
DATA FOR STARTING
REGISTER ADDRESS
D14
18
XXX
CW
0
16
D15
X
17
t
6
D14
X
18
16-BIT READBACK DATA
D1
31
D13
X
19
D0
32
D15
33
D14
REGISTER ADDRESS
34
DATA FOR NEXT
D2
X
30
AD7879/AD7889
D1
X
t
8
31
t
7
D0
X
32
D1
47
XXX
D0
48
D15
49