Texas Instruments ADS79 EVM-PDK Series, Manual

Page: 33 / 77

CS
Sample
CHx
Sample
CHy
SCLK
Sample
CH4
Sample
CH7
Data CHx Data CHy Data CH4
SDO
t
CYCLE
Select CH4 Select CH7 Select CH9 SDI
Frame N Frame (N + 1) Frame (N + 2)
33
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Device Functional Modes (continued)
(1) GPIO 1 to 3 are available only in TSSOP packaged devices. QFN device offers GPIO 0 only.
Figure 51 shows an example in which manual mode is used to scan channels 4, 7, and 9. The command to
select channel 4 (CH4) is issued in the Nth frame and the data corresponding to CH4 is available in the (N + 2)th
frame. Internally, the SDI command is parsed and on the rising edge of CS of the (N+1)th frame and the MUX
switches accordingly on the second falling edge of SCLK in this frame. On the rising edge of CS of the (N+2)th
frame, the input signal for CH4 is sampled and the ADC sends the conversion data in this third frame. The
device follows the same steps and the ADC sends the conversion data for CH7 and CH9 in the subsequent two
frames.
Figure 51. Example Manual Mode Timing Diagram
Table 1. Mode Control Register Settings for Manual Mode
BITS
RESET
STATE LOGIC
STATE
FUNCTION
DI15-12 0001 0001 Selects Manual Mode
DI11 0 1 Enables programming of bits DI06-00.
0 Device retains values of DI06-00 from the previous frame.
DI10-07 0000 This four bit data represents the address of the next channel to be selected in the next frame. DI10: MSB and
DI07: LSB. For example, 0000 represents channel- 0, 0001 represents channel-1 and so forth.
DI06 0 0 Selects 0 to V
REF
input range (Range 1)
1 Selects 0 to 2xV
REF
input range (Range 2)
DI05 0 0 Device normal operation (no powerdown)
1 Device powers down on 16th SCLK falling edge
DI04 0
0
SDO outputs current channel address of the channel on DO15..12 followed by 12 bit conversion
result on DO11..00.
1 GPIO3-GPIO0 data (both input and output) is mapped onto DO15-DO12 in the order shown below.
Lower data bits DO11-DO00 represent 12-bit conversion result of the current channel.
DOI5 DOI4 DOI3 DOI2
GPIO3
(1)
GPIO2
(1)
GPIO1
(1)
GPIO0
(1)
DI03-00 0000 GPIO data for the channels configured as output. Device will ignore the data for the channel which is configured
as input. SDI bit and corresponding GPIO information is given below
DI03 DI02 DI01 DI00
GPIO3
(1)
GPIO2
(1)
GPIO1
(1)
GPIO0
(1)