Difference between revisions of "83Plus:Ports:14"
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'''Function:''' Flash Write-Lock Control | '''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 [[: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 | + | * '''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 ( | + | 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. | ||
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.
