Configuration Mode Transmit Communications Protocol - Analog Devices ADXL180 iMEMS Manual

TRANSMITTED
CONFIGURATION MODE TRANSMIT
COMMUNICATIONS PROTOCOL
In configuration mode, the ADXL180 transmits the configura-
tion mode register data through the current mode Manchester
encoded serial port. The configuration mode protocol is fixed
regardless of the actual settings of the configuration registers
(RAM or OTP). The transmit communication protocol used by
the ADXL180 in configuration mode is
•
Manchester-1 data encoding
•
Two start bits (10b)
•
4-bit configuration mode register address field
•
8-bit configuration mode register data field
•
3-bit state vector field (101b)
•
One parity bit (even)
•
Synchronization pulse disabled
•
Auto-zero disabled
•
Data is transmitted LSB first
START STATE
FIRST
BITS VECTOR
1 0 0 1 2 0
Figure 36. Configuration Mode Transmit Data Frame
Rev. 0 | Page 45 of 56
DATA FRAME (18 BITS)
DATA
1 2 3 4 5 6 7 0
This is an 18-bit protocol (including the two start bits). Although
similar to the ADIFX protocol, it is different in that parity, and
not CRC, is used as the error checking code. This distinguishes
configuration mode messages from normal operation messages.
Figure 36 shows the configuration mode data frame format.
Table 42 shows the configuration mode transmit data bit mapping.
Excluding the two start bits, the word is 16 bits long. Data Bit
DB15 (transmitted last) is the parity bit. The configuration
mode transmit parity is even. The parity bit is set to either 1 or
0 to make the total number of 1s in the 16-bit word an even
number. Data Bits[DB14:DB11] are the four configuration
mode register address bits. The following eight data bits, DB10
through DB3, are the eight configuration mode register data
bits. The next three bits, DB2 through DB0, are the state vector
bits. In the configuration mode, the state vector is 101b. This
data frame format is different from the ADIFX format.
ADDRESS P
1 2 3 0
ADXL180