Datasheet

Instructions M93S46-W M93S56-W M93S66-W
20/37 DocID5124 Rev 6
Protection register read
The Protection Register Read (PRREAD) instruction outputs, on Serial Data Output (Q), the
content of the Protection Register, followed by the Protection Flag bit. The Protection
Enable (PRE) signal must be driven High before and during the instruction.
As with the Read Data from Memory (READ) instruction, a dummy 0 bit is output first. Since
it is not possible to distinguish between the Protection Register being cleared (all 1s) or
having been written with all 1s, the user must check the Protection Flag status (and not the
Protection Register content) to ascertain the setting of the memory protection.
Protection register enable
The Protection Register Enable (PREN) instruction is used to authorize the use of
instructions that modify the Protection Register (PRWRITE, PRCLEAR, PRDS). The
Protection Register Enable (PREN) instruction does not modify the Protection Flag bit value.
Note: A Write Enable (WEN) instruction must be executed before the Protection Register Enable
(PREN) instruction. Both the Protection Enable (PRE) and Write Enable (W) signals must
be driven High during the instruction execution.
Protection register clear
The Protection Register Clear (PRCLEAR) instruction clears the address stored in the
Protection Register to all 1s, so that none of the memory is write-protected by the Protection
Register. However, it should be noted that all the memory remains protected, in the normal
way, using the Write Enable (WEN) and Write Disable (WDS) instructions.
The Protection Register Clear (PRCLEAR) instruction clears the Protection Flag to 1. Both
the Protection Enable (PRE) and Write Enable (W) signals must be driven High during the
instruction execution.
Note: A Protection Register Enable (PREN) instruction must immediately precede the Protection
Register Clear (PRCLEAR) instruction.
Protection register write
The Protection Register Write (PRWRITE) instruction is used to write an address into the
Protection Register. This is the address of the first word to be protected. After the Protection
Register Write (PRWRITE) instruction has been executed, all memory locations equal to
and above the specified address are protected from writing.
The Protection Flag bit is set to 0, and can be read with Protection Register Read
(PRREAD) instruction.
Both the Protection Enable (PRE) and Write Enable (W) signals must be driven High during
the instruction execution.
Note: A Protection Register Enable (PREN) instruction must immediately precede the Protection
Register Write (PRWRITE) instruction, but it is not necessary to execute first a Protection
Register Clear (PRCLEAR).
Protection register disable
The Protection Register Disable (PRDS) instruction sets the One Time Programmable
(OTP) bit.
This instruction is a ONE TIME ONLY instruction which latches the Protection Register
content, this content is therefore unalterable in the future. Both the Protection Enable (PRE)