25CSM04 datasheet(32/55 Pages) MICROCHIP

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25CSM04

DS20005817D-page 32

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9.2.2

DETERMINING THE LOCK STATE

OF THE SECURITY REGISTER

To determine whether or not the user-programmable

lockable ID page of the Security register is locked, the

25CSM04 includes a CHLK instruction to check the lock

state. To determine the lock status, the opcode 83h

must be clocked into the device on the SI line. The

address bit A10 must be equal to logic ‘1’ while the

other address bits are “don’t care”. Data bit 0 of the

data byte clocked out on the SO line determines the

lock state, the other bits of the data byte are “don’t care”

bits. A data response of xxxxxxx1b indicates the

region is locked, while a xxxxxxx0b response

indicates that the region is not locked.

FIGURE 9-5:

CHECK SECURITY REGISTER LOCK (CHLK) SEQUENCE

Note 1: A23 through A0 are “don’t care” bits, except A10 which must be a logic ‘1’.

SCK

234

567

910 11 12

40 41

10 0 0 00 11

A A A

RDEX Opcode (83h)

Address Bits A23-A0(1)

XXX X X X

Data Out

MSb

High-Impedance

D5 D4 D3 D2 D1 D0

SCK

234

567

910 11 12

40 41

xxxxxxx1b = Locked

xxxxxxx0b = Unlocked

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