Difference between revisions of "83Plus:Ports:14"
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=== Write Values === | === Write Values === | ||
| − | * Write 00h to lock the flash. Write 01h to unlock it | + | * Write 00h to lock the flash. Write 01h to unlock it. |
== Comments == | == Comments == | ||
Revision as of 09:57, 9 August 2011
| This port is protected, which means user programs cannot ordinarily write to it directly. |
Synopsis
Port Number: 14h
Function: Flash Write-Lock Control
This port controls whether or not the Flash ROM chip will accept write/erase instructions.
Read Values
- 83+ Basic only: Reads absolutely nothing of any significance.
- 83+ SE/84+ only: Reads 0 if the flash is locked, 1 if the flash is unlocked.
Write Values
- Write 00h to lock the flash. Write 01h to unlock it.
Comments
When the flash chip is locked, then write/erase instructions are rejected. In addition, protected pages cannot be read. There is only one protected page. On the normal 83+, this is page 1Eh. On the normal 84+, it is 3Eh. On the 83+ SE and 84+ SE it is 7Eh. This page holds the certification data, which includes ID number, validation number, application authorizations, public keys, and other related data.
Other protected ports may be written to from any area (unprivledged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.
