FS5502 datasheet(80/113 Pages) NXP

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NXP Semiconductors

FS5502

High voltage PMIC with multiple SMPS and LDO

20.3 Cyclic redundant check

An 8 bit CRC is required for each Write and Read I2C command. Computation of a cyclic

redundancy check is derived from the mathematics of polynomial division, modulo two.

The CRC polynomial used is x^8+x^4+x^3+x^2+1 (identified by 0x1D) with a SEED value

of hexadecimal '0xFF'

The following table shows an example of CRC encoding HW implementation:

CRC calculation using XOR:

CRC_7 = XOR (B38, B35, B32, B31, B24, B23, B22, B20, B17, B13, B12, B11, 1, 1, 1)

CRC_6 = XOR (B37, B34, B23, B22, B21, B19, B16, B12, B11, B10, 1, 1)

CRC_5 = XOR (B39, B36, B33, B30, B29, B22, B21, B20, B18, B15, B11, B10, B9, 1, 1, 1)

CRC_4 = XOR (B39, B38, B35, B32, B29, B28, B21, B20, B19, B17, B14, B10, B9, B8, 1, 1, 1, 1)

CRC_3 = XOR (B37, B35, B34, B32, B28, B27, B24, B23, B22, B19, B18, B17, B16, B12, B11, B9, B8, 1, 1, 1, 1)

CRC_2 = XOR (B39, B38, B36, B35, B34, B33, B32, B27, B26, B24, B21, B20, B18, B16, B15, B13, B12 B10, B8, 1,1,1,1,1,1,1)

CRC_1 = XOR (B37, B34, B33, B26, B25, B24, B22, B19, B15, B14, B13, B9, 1, 1, 1)

CRC_0 = XOR (B39, B36, B33, B32, B25, B24, B23, B21, B18, B14, B13, B12, B8, 1, 1, 1, 1)

CRC results examples:

• Main I2C device address: 0x20

• Fail-safe I2C device address: 0x21

aaa-035373

1*1

0*X

1*X2

1*X3

1*X4

0*X5

0*X6

0*X7

1*X8

Input

data

Figure 28. CRC encoder example

Device address,

R/W, 8 bit (Hex)

00, Register

address, 8 bit

(Hex)

Data MSB, 8 bit

(Hex)

Data LSB, 8 bit

(Hex)

CRC, 8 bit

0x40

0x02

0x00

0x31

0x42

0x01

0xD0

0x0D

0x8C

Table 76. CRC results example

FS5502

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Product data sheet

Rev. 4 — 27 October 2021

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