MCP3910 datasheet(77/90 Pages) MICROCHIP

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 2012-2020 Microchip Technology Inc.

DS20005116D-page 77

MCP3910

9.9

SECURITY Register – Password

and CRC-16 on Register Map

Name

Bits

Address

Cof

LOCK/CRC

0x1F

R/W

SECURITY: LOCK/CRC REGISTER

R/W-1

R/W-0

R/W-1

R/W-0

R/W-1

R/W-0

R/W-1

LOCK[7:0]

bit 23

bit 16

R/W-0

CRCREG[15:8]

bit 15

bit 8

R/W-0

CRCREG[7:0]

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 23-16

LOCK[7:0]:

Lock Code for Writable Part of Register Map bits

LOCK[7:0] = PASSWORD = 0xA5 (default value): The entire register map is writable. The

CRCREG[15:0] bits and the CRC interrupt are cleared. No CRC-16 checksum on register map is

calculated.

LOCK[7:0] are different than 0xA5: The only writable register is the LOCK/CRC register. All other reg-

isters will appear as undefined while in this mode. The CRCREG checksum is calculated continuously

and can generate interrupts if the CRC interrupt EN_INT bit has been enabled. If a write to a register

needs to be performed, the user needs to unlock the register map beforehand by writing 0xA5 to the

LOCK[7:0] bits.

bit 15-0

CRCREG[15:0]:

CRC-16 Checksum Calculated with Writable Part of Register Map as Message bits

This is a read-only 16-bit code. This checksum is continuously recalculated and updated every

12 DMCLK periods. It is reset to its default value (0x0000) when LOCK[7:0] = 0xA5.

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