![](http://datasheet.mmic.net.cn/Semtech/XE8802MI035LF_datasheet_100001/XE8802MI035LF_118.png)
Semtech 2006
www.semtech.com
17-6
XE8802 Sensing Machine Data Acquisition MCU
with ZoomingADC and LCD driver
Cont’
Bit Position
Register
Name
7
6
5
4
3
2
1
0
RegAcCfg2
Default values:
FIN[1:0]
00
PGA2_GAIN[1:0]
00
PGA2_OFFSET[3:0]
0000
RegAcCfg3
Default values:
PGA1_G
0
PGA3_GAIN[6:0]
0000000
RegAcCfg4
Default values:
0
PGA3_OFFSET[6:0]
0000000
RegAcCfg5
Default values:
BUSY
0
DEF
0
AMUX[4:0]
00000
VMUX
0
With:
OUT
: (r) digital output code of the analog-to-digital converter. (MSB = OUT[15])
START
: (w) setting this bit triggers a single conversion (after the current one is finished). This bit always reads back 0.
SET_NELC
: (rw) sets the number of elementary conversions to 2
SET_NELC[1:0]
. To compensate for offsets, the input signal
is chopped between elementary conversions (1,2,4,8).
SET_OSR
: (rw) sets the over-sampling rate (OSR) of an elementary conversion to 2
(3+SET_OSR[2:0])
. OSR = 8, 16, 32, ...,
512, 1024.
CONT
: (rw) setting this bit starts a conversion. A new conversion will automatically begin as long as the bit remains at 1.
TEST
: bit only used for test purposes. In normal mode, this bit is forced to 0 and cannot be overwritten.
IB_AMP_ADC
: (rw) sets the bias current in the ADC to 0.25*(1+ IB_AMP_ADC[1:0]) of the normal operation current (25,
50, 75 or 100% of nominal current). To be used for low-power, low-speed operation.
IB_AMP_PGA
: (rw) sets the bias current in the PGAs to 0.25*(1+IB_AMP_PGA[1:0]) of the normal operation current (25,
50, 75 or 100% of nominal current). To be used for low-power, low-speed operation.
ENABLE
: (rw) enables the ADC modulator (bit 0) and the different stages of the PGAs (PGAi by bit i=1,2,3). PGA stages
that are disabled are bypassed.
FIN
: (rw) These bits set the sampling frequency of the acquisition chain. Expressed as a fraction of the oscillator frequency,
the sampling frequency is given as: 00
1/4 fRC, 01
1/8 fRC, 10
1/32 fRC, 11
~8kHz.
PGA1_GAIN
: (rw) sets the gain of the first stage: 0
1, 1
10.
PGA2_GAIN
: (rw) sets the gain of the second stage: 00
1, 01
2, 10
5, 11
10.
PGA3_GAIN
: (rw) sets the gain of the third stage to PGA3_GAIN[6:0]
1/12.
PGA2_OFFSET
: (rw) sets the offset of the second stage between –1 and +1, with increments of 0.2. The MSB gives the sign
(0
→ positive, 1 → negative); amplitude is coded with the bits PGA2_OFFSET[5:0].
PGA3_OFFSET
: (rw) sets the offset of the third stage between –5.25 and +5.25, with increments of 1/12. The MSB gives the
sign (0
→ positive, 1 → negative); amplitude is coded with the bits PGA3_OFFSET[5:0].
BUSY
: (r) set to 1 if a conversion is running.
DEF
: (w) sets all values to their defaults (PGA disabled, max speed, nominal modulator bias current, 2 elementary
conversions, over-sampling rate of 32) and starts a new conversion without waiting the end of the preceding one.
AMUX(4:0):
(rw) AMUX[4] sets the mode (0
4 differential inputs, 1
7 inputs with A(0) = common reference)
AMUX(3)
sets the sign (0
straight, 1
cross) AMUX[2:0] sets the channel.
VMUX
: (rw) sets the differential reference channel (0
R(1)
and R(0), 1
R(3)
and R(2)).
(r = read; w = write; rw = read & write)
Not
Recommended
for
New
Designs