Difference between revisions of "83Plus:Ports:14"

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'''Function:''' Flash Write-Lock Control
 
'''Function:''' Flash Write-Lock Control
  
This port controls whether or not the Flash ROM chip will accept write/erase instructions.
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Writing to this port controls whether or not the Flash ROM chip will accept write/erase instructions. However, writes are only accepted after the [[:Category:83Plus:Ports:By Address:Protected|unlock sequence]] is executed from a protected page.
  
 
=== Read Values ===
 
=== Read Values ===
 
* '''83+ Basic only''': Mirror of [[83Plus:Ports:04|port 04h]].
 
* '''83+ Basic only''': Mirror of [[83Plus:Ports:04|port 04h]].
* '''83+ SE/84+ only''': Reads 0 if the flash is locked, 1 if the flash is unlocked.
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* '''83+ SE/84+ only''': Reads 0 zero.
  
 
=== Write Values ===
 
=== Write Values ===
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== Comments ==
 
== 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.
 
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.
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Use bit 2 of [[83Plus:Ports:02|port 2]] to check if flash is unlocked.
  
 
Other protected ports may be written to from any area (unprivileged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.
 
Other protected ports may be written to from any area (unprivileged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.

Latest revision as of 15:40, 11 May 2014

This port is protected, which means user programs cannot ordinarily write to it directly.

Synopsis

Port Number: 14h

Function: Flash Write-Lock Control

Writing to this port controls whether or not the Flash ROM chip will accept write/erase instructions. However, writes are only accepted after the unlock sequence is executed from a protected page.

Read Values

  • 83+ Basic only: Mirror of port 04h.
  • 83+ SE/84+ only: Reads 0 zero.

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.

Use bit 2 of port 2 to check if flash is unlocked.

Other protected ports may be written to from any area (unprivileged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.