83Plus:Ports:14 - Revision history

Dr. D'nar at 22:40, 11 May 2014

2014-05-11T22:40:56Z

JosJuice: /* Comments */

2013-06-27T18:43:46Z

‎Comments

Thepenguin77 at 04:30, 28 October 2011

2011-10-28T04:30:32Z

Sircmpwn: /* Write Values */

2011-08-09T16:57:07Z

‎Write Values

Sircmpwn: Updated info about protected ports

2011-08-09T16:55:58Z

Updated info about protected ports

Aquanight at 00:49, 2 April 2005

2005-04-02T00:49:34Z

FloppusMaximus at 21:14, 30 March 2005

2005-03-30T21:14:20Z

FloppusMaximus at 05:19, 30 March 2005

2005-03-30T05:19:18Z

FloppusMaximus at 21:54, 29 March 2005

2005-03-29T21:54:35Z

FloppusMaximus: categorized

2005-03-29T21:40:37Z

categorized

@@ Line 7: / Line 7: @@
 '''Function:''' Flash Write-Lock Control
-This port controls whether or not the Flash ROM chip will accept write/erase instructions.
+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 ===
 * '''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.
+* '''83+ SE/84+ only''': Reads 0 zero.
 === Write Values ===
@@ Line 18: / Line 18: @@
 == 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 (unprivileged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.

← Older revision		Revision as of 18:43, 27 June 2013
Line 19:		Line 19:
	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.	+	Other protected ports may be written to from any area (unprivileged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.

@@ Line 10: / Line 10: @@
 === Read Values ===
-* '''83+ Basic only''': Reads absolutely nothing of any significance.
+* '''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.

@@ Line 14: / Line 14: @@
 === Write Values ===
-* Write 00h to lock the flash. Write 01h to unlock it, but note that writes to this port are only accepted from privileged ROM pages. See Comments for what the privileged pages are.
+* Write 00h to lock the flash. Write 01h to unlock it.
 == Comments ==

@@ Line 19: / Line 19: @@
 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.
-The flash can only be locked and unlocked from privileged ROM pages. The privileged ROM pages are two utility code pages and one or two boot code pages. On the normal 83+ the pages are 1Ch, 1Dh, and 1Fh. On the normal 84+ the pages are 3Ch, 3Dh, and 3Fh. On the 83+ SE the pages are 7Ch, 7Dh, and 7Fh.  On the 84+ SE the pages are 6Fh, 7Ch, 7Dh, and 7Fh.
+Other protected ports may be written to from any area (unprivledged ROM, RAM, etc) without requiring a special sequence once Flash is unlocked.
-−
-Finally a specific sequence of instructions must be executed (all of them from a privileged page, with no interruptions) before the port will finally listen. The sequence is:
-−
- <nowiki>nop
-nop
-im 1
-di</nowiki>
-−
-''Note: it is still unclear whether all or only part of this sequence is actually required. But since TI uses this exact sequence every time, it is best to play it safe and use the exact sequence.''
-−
-After this sequence, use out (14h), a to write the port.
-−
-Note that as a side effect, interrupts are disabled, and standard interrupt handling (mode 1) is selected. To ensure this sequence runs uninterrupted, however, you should use di prior to executing this sequence. If an interrupt fired in the middle of it, it would mess up the whole thing. Also, the A register must be previously set to the correct value (0 to lock, 1 to unlock).
-−
-''Side note: TI also adds an additional di after the write. Sources inform me, however, that this is not required.''
-−
-== Example ==
- <nowiki>ld a, 1 ;Unlock
-di ;Make sure we don't get interrupted.
-nop
-nop
-im 1
-di
-out (14h), a
-−
-xor a ;Lock.
-di
-nop
-nop
-im 1
-di
-out (14h), a</nowiki>

@@ Line 1: / Line 1: @@
 [[Category:83Plus:Ports:By_Address:Protected|14 - Flash Control]] [[Category:83Plus:Ports:By_Address|14 - Flash Control]] [[Category:83Plus:Ports:By_Name|Flash Control]]
 == Synopsis ==
 '''Port Number:''' 14h