Data Sheet - Freescale Semiconductor

The status bit messages and message priority are listed in Table 65. Reference Section 5 for details on exception handling.
Table 65. Periodic Data Collection Mode Status field definitions
s[3:0] Description DEVSTAT State
Error
Priority
Acceleration Data Field Value
0 0 0 0 Normal mode N/A NA Acceleration Data
0 0 0 1 Offset Error OFFSET_ERR set 4 Acceleration Data
0 0 1 0 Freescale OTP Array Error F_OTP_ERR set 1 Error Code
0 0 1 1 User OTP Array Error U_OTP_ERR set 2 Error Code
0 1 0 0
User Read/Write Array
Error
U_RW_ERR set 3 Error Code
0 1 0 1 Reserved N/A 8 Acceleration Data
0 1 1 0 Reserved N/A 9 Acceleration Data
0 1 1 1 Oscillator Training Error OSCTRAIN_ERR set 6 Acceleration Data
1 0 0 0
Self-test Activation
Incomplete
ST_INCMPLT set 5 Acceleration Data
1 0 0 1 Reserved N/A 7 Acceleration Data
1 0 1 0 Reserved N/A 10 Acceleration Data
1 0 1 1 Reserved N/A 11 Acceleration Data
1 1 0 0 Reserved N/A 12 Acceleration Data
1 1 0 1 Reserved N/A 13 Acceleration Data
1 1 1 0 Reserved N/A 14 Acceleration Data
1 1 1 1 Test mode active TESTMODE set 15 Error Code
4.3.2.3 Error checking
The device calculates a CRC on the entire response. Data is entered into the CRC calculator MSB first, consistent with the
transmission order of the message.
The CRC Encoding procedure is:
1. A seed value is preset into the least significant bits of the shift register.
2. Using a serial CRC calculation method, the transmitter rotates the transmitted message into the least significant bits of
the shift register, MSB first.
3. Following the transmitted message, the transmitter feeds eight zeros into the shift register, to match the length of the
CRC.
4. When the last zero is fed into the input adder, the shift register contains the CRC.
5. The CRC is transmitted.
The CRC polynomial is specified in the PDCMCRCPLY register. The CRC default polynomial and Seed for Command and
Response Mode are shown in Table 66.
Table 66. Periodic Data Collection Mode Response CRC
Some example CRC calculations are shown in Table 67.
MMA27XXW
Mode Default Polynomial Seed
Periodic Data Collection Mode x 8 + x 5 + x 3 + x 2 + x + 1 SOURCEID[7:0]
Table 67. Periodic Data Collection Mode - CRC Calculation Examples
Source Identification
(4 Bits)
Keep Alive Counter
(2 Bits)
Status (4 Bits)
Acceleration Data
(10 Bits)
8-bit CRC
0x1 0x3 0x0 0x1FF 0xD6
0x2 0x2 0x0 0x1FE 0x70
0x3 0x1 0x0 0x20D 0xB0
0x4 0x0 0x0 0x1EA 0x5F
Sensors
74 Freescale Semiconductor, Inc.