Analog Devices ADXL180 iMEMS, Manual

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ADXL180
Rev. 0 | Page 33 of 56
Table 32. Phase 2 Mode 2 User Bit Mapping
User Bit Device Data Bit Name
U11 SYEN
U10 RG2
U09 RG1
U08 RG0
U07 UD7
U06 UD6
U05 UD5
U04 UD4
U03 UD3
U02 UD2
U01 UD1
U00 UD0
Mode 3
Device Data
In Phase 2 Mode 3, the 10-bit data codes, −512 (0x200) to −481
(0x21F), are used to transmit the device data. The data coding
is shown in Table 34
and in Figure 25. One 4-bit nybble of the
device data (encoded as one of 16 nybble codes) is transmitted
in each 10-bit message. The number of the data nybble is identi-
fied by the preceding nybble number (NN) code as detailed in
Table 33. This allows a total of (16 × 4) = 64 unique bits of device
data to be transmitted during Phase 2. Each message is repeated
32 times for each nybble number. The specific meaning of each
data nybble is defined in Table 33. The total number of messages
transmitted during Phase 2 in Mode 3 is (32 × 16) = 512.
User Register (UREG)
The User Register UREG[7:0], in Mode 3 transmit during
Nybble 7 (UREG[7:4]) and Nybble 8 (UREG[3:0]).
Use with State Vector Enabled
When Mode 3 is selected with the state vector enabled and the
auto-zero not enabled, the full range sensor data coding is used
(see the Data Frame Transmission Format section). Therefore,
the positive and negative full-scale ends of the sensor data range
overlap with the device data and status data codes. The state vector
distinguishes between the types of transmitted data. The state
vector identifies the device data (state vector = 001b) and status
codes as status/error data (state vector = 110b). Normal opera-
tion sensor data has a state vector of 000b (see Table 19).
Illegal Configuration: Mode 3 and 8-Bit Data
A configuration error is flagged if Phase 2 Mode 3 is selected
and the configuration register is programmed to select the 8-bit
data mode. In this case, the error state is entered immediately
instead of Phase 1. See the Error Detection section for more
information.
PHASE 1 PHASE 2 PHASE 3
NN1
DATA1 NN1 DATA1
32 MESSAGES
NN2 DATA2 NN2 DATA2 NN16
DATA
16
NN16
DATA
16
32 MESSAGES 32 MESSAGES
07
54
4-
0
46
Figure 25. Mode 3 Device Data Transmission
Table 33. Phase 2 Mode 3 Device Data Mapping
Device Data Nybble No. Definition Binary Code Nybble Sent
1
1
Protocol ID 001 0011
2 Number of nybbles sent 16 10000 0000
3 Manufacturer Analog Devices 101 1010
4 Sensor type Accelerometer 00001 0001
5 Sensor range
2
100 g 0000 0000
50 g 0001 0001
200 g 0010 0010
Other 0011 0011
6 BDE and RS RS = 0, BDE = 0 0000 0000
RS = 0, BDE = 1 0001 0001
RS = 1, BDE = 0 0010 0010
RS = 1, BDE = 1 0011 0011
7 User data (UD Bits[7:4]) 0 to 255 XXXX 3 XXXX
8 User data (UD Bits[3:0]) 0 to 255 XXXX XXXX
9 Serial number (Bits[31:28]) XXXX XXXX
10 Serial number (Bits[27:24]) XXXX XXXX