84PCE:Ports:0028

Synopsis

Port Number: 0028

Function: Flash Protection Status

Details

Flash is unlocked if both bits 2 and 3 of this port are set.

Bit [0]

Latches value written, no apparent effect.

Used by OS on Python Edition.

Bit [1]

Always 0, writes do not latch.

Bit [2]

Can be written freely (under the usual privileged port constraints).

Bit [3]

Can be cleared by writing a 0. Gets cleared any time unprivileged code is executed or port 6 bit 2 is reset. Fetching a flash unlock sequence (F31800F3ED7EED56ED3928ED3828CB57) that ends in privileged flash while port 6 bit 2 is set is the only way to set it.

Bits [7:4]

Writes do not latch, no apparent effect.