BQ2060SS Datasheet, PDF (18/59 Pages) Texas Instruments – SBS V1.1-COMPLIANT GAS GAUGE IC

bq2060
SLUS035E – JANUARY 2000 – REVISED OCTOBER 2005
www.ti.com
In the Write Word protocol, the bq2060 receives the PEC after the last byte of data from the host. If the host
does not support PEC, the last byte of data is followed by a STOP condition. After receipt of the PEC, the
bq2060 compares the value to its calculation. If the PEC is correct, the bq2060 responds with an
ACKNOWLEDGE. If is not correct, the bq2060 responds with a NOT ACKNOWLEDGE and sets an error code.
Figure 8. SMBus Communication Protocol Without PEC
Figure 9. SMBus Communication Protocol With PEC
In the Read Word and Block Read, the host generates an ACKNOWLEDGE after the last byte of data is sent by
the bq2060. The bq2060 then sends the PEC and the host acting as a master-receiver generates a NOT
ACKNOWLEDGE and a STOP condition.
PEC Calculation
The basis of the PEC calculation is an 8-bit cyclic redundancy check (CRC-8) based on the polynomial C(X) = X⁸
+ X² + X¹ + 1. The PEC calculation includes all bytes in the transmission, including address, command, and data.
The PEC calculation does not include ACKNOWLEDGE, NOT ACKNOWLEDGE, START, STOP, and repeated
START bits.
For example, the host requests RemainingCapacity() from the bq2060. This includes the host following the Read
Word protocol. The bq2060 calculates the PEC based on the following 5 bytes of data, assuming that the
remaining capacity of the battery is 1001 mAh.
• Battery Address with R/W = 0: 0x16
• Command Code for RemainingCapacity(): 0x0f
18