Datasheet

ADS8634
ADS8638
SBAS541A –MAY 2011– REVISED AUGUST 2011 www.ti.com
PAGE 0 REGISTER DESCRIPTIONS (ADS8634)
This section provides bit-by-bit descriptions of each page 0 register. As described earlier, the device registers are
mapped to two pages: page 0 and page 1. Page 0 is selected by default at power-up and after reset. Any
register read/write action while on page 0 addresses the page 0 registers. Writing 01h to register address 7Fh
selects page 1 for any further register operations.
Channel Sequencing Control Registers for the ADS8634
There are two modes for channel sequencing: auto and manual mode. In auto-scan mode, the device
automatically scans the preselected channels in chronological order; a new channel is selected for every
conversion. In manual mode, the channel is selected for the next conversion. In both modes, the preselected
signal range is considered for each channel independently; however, the range can be temporarily overriden.
Manual: Manulal Mode Register (Address = 04h; Page 0)
7 6 5 4 3 2 1 0
Sel Temp
0 Channel Select[1:0] X
(1)
Range Select[2:0]
Sensor
(1) X = don't care.
This register selects device operation in manual scan mode, selects channel for next conversion, allows the
preselected signal range for the next conversion to be temporarialy overridden, and enables the device
temperature to be read.
Bit 7 Must always be set to '0'
Bits[6:5] Channel Select[1:0]
These bits select the channel for acquisition during the next frame.
For example, if this register is written in frame number n, then the addressed channel signal is acquired in frame
number n + 1 and the conversion result is available in frame number n + 2.
00 = Channel 0
01 = Channel 1
10 = Channel 2
11 = Channel 3
Bit 4 Don't care (can be 1 or 0); this bit has no function assigned
Bits[3:1] Range Select[2:0]
These bits select the signal range for the channel acquired in the next frame.
For example, if this register is written in frame number n, then the selected range is applicable for frame number n
+ 1. This is a dynamic range selection and overrides selection through the configuration registers (addresses 10h to
13h, page 0) only for the next frame.
000 = Ranges as selected through the configuration registers (address 10h to 13h, page 0)
001 = Range is set to ±10V
010 = Range is set to ±5V
011 = Range is set to ±2.5V
100 = Reserved; do not use this setting
101 = Range is set to 0V to 10V
110 = Range is set to 0V to 5V
111 = Powers down the device immediately after the 16th SCLK falling edge
Bit 0 Sel Temp Sensor
This bit selects the temperature sensor for acquisition in the next frame.
This selection overrides channel selection through bits[6:4]. Range selection is not applicable for the temperature
sensor.
0 = Next conversion as per selection through bits[3:1]
1 = Device selects the temperature sensor for acquisition in the next frame
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