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

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(Write Values)
 
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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''': Reads absolutely nothing of any significance.
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* '''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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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.
  
Other protected ports may be written to from any area (unprivledged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.
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Use bit 2 of [[83Plus:Ports:02|port 2]] to check if flash is unlocked.
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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.