83Plus:State of the calculator at boot - Revision history

Dr. D'nar: Changed display name

2012-02-17T21:03:30Z

Changed display name

Sircmpwn at 16:51, 28 November 2011

2011-11-28T16:51:14Z

Thepenguin77 at 02:23, 26 November 2011

2011-11-26T02:23:40Z

Thepenguin77 at 02:09, 26 November 2011

2011-11-26T02:09:43Z

Thepenguin77: Created page with 'This page is dedicated to what happens right when the calculator begins to execute code. For now, all the information is about the 84+. When someone does some boot code work wit…'

2011-11-26T02:03:17Z

Created page with 'This page is dedicated to what happens right when the calculator begins to execute code. For now, all the information is about the 84+. When someone does some boot code work wit…'

New page

This page is dedicated to what happens right when the calculator begins to execute code.

For now, all the information is about the 84+. When someone does some boot code work with the 83+, this page will have to be updated.

==Registers==
All registers are 00h. However, if you are writing a boot code, you should still initialize the variables on the off chance that one is not 00h, or if someone jumps to your boot code.

==Port Values==
These port values were all found on an 84+SE hardware revision M with a [[83Plus:Ports:15|port 15]] value of 55h.

{| cellspacing="0" border="1"
|
{|
|Port||Value
|-
|00h||03h
|-
|01h||FFh
|-
|02h||E3h
|-
|03h||00h
|-
|04h||08h
|-
|05h||00h
|-
|06h||00h
|-
|07h||00h
|-
|08h||00h
|-
|09h||20h
|-
|0Ah||00h
|-
|0Bh||00h
|-
|0Ch||00h
|-
|0Dh||00h
|-
|0Eh||00h
|-
|0Fh||00h
|}
|
{|
|Port||Value
|-
|10h||FFh
|-
|11h||FFh
|-
|12h||FFh
|-
|13h||FFh
|-
|14h||00h
|-
|15h||55h
|-
|16h||00h
|-
|17h||00h
|-
|18h||00h
|-
|19h||00h
|-
|1Ah||00h
|-
|1Bh||00h
|-
|1Ch||00h
|-
|1Dh||00h
|-
|1Eh||00h
|-
|1Fh||00h
|}
|
{|
|Port||Value
|-
|20h||00h
|-
|21h||33h
|-
|22h||00h
|-
|23h||00h
|-
|24h||00h
|-
|25h||00h
|-
|26h||00h
|-
|27h||00h
|-
|28h||00h
|-
|29h||00h
|-
|2Ah||00h
|-
|2Bh||00h
|-
|2Ch||00h
|-
|2Dh||00h
|-
|2Eh||00h
|-
|2Fh||00h
|}
|
{|
|Port||Value
|-
|30h||00h
|-
|31h||00h
|-
|32h||00h
|-
|33h||00h
|-
|34h||00h
|-
|35h||00h
|-
|36h||00h
|-
|37h||00h
|-
|38h||00h
|-
|39h||00h
|-
|3Ah||00h
|-
|3Bh||00h
|-
|3Ch||FFh
|-
|3Dh||FFh
|-
|3Eh||FFh
|-
|3Fh||FFh
|}
|
{|
|Port||Value
|-
|40h||00h
|-
|41h||00h
|-
|42h||00h
|-
|43h||00h
|-
|44h||00h
|-
|45h||00h
|-
|46h||00h
|-
|47h||00h
|-
|48h||00h
|-
|49h||18h
|-
|4Ah||06h
|-
|4Bh||00h
|-
|4Ch||22h
|-
|4Dh||A9h
|-
|4Eh||00h
|-
|4Fh||00h
|}
|
{|
|Port||Value
|-
|50h||00h
|-
|51h||00h
|-
|52h||00h
|-
|53h||00h
|-
|54h||02h
|-
|55h||1Fh
|-
|56h||00h
|-
|57h||00h
|-
|58h||00h
|-
|59h||00h
|-
|5Ah||00h
|-
|5Bh||00h
|-
|5Ch||00h
|-
|5Dh||00h
|-
|5Eh||00h
|-
|5Fh||00h
|}
|
{|
|Port||Value
|-
|60h||00h
|-
|61h||00h
|-
|62h||00h
|-
|63h||00h
|-
|64h||00h
|-
|65h||00h
|-
|66h||00h
|-
|67h||00h
|-
|68h||00h
|-
|69h||18h
|-
|6Ah||06h
|-
|6Bh||00h
|-
|6Ch||22h
|-
|6Dh||A9h
|-
|6Eh||00h
|-
|6Fh||00h
|}
|
{|
|Port||Value
|-
|70h||00h
|-
|71h||00h
|-
|72h||00h
|-
|73h||00h
|-
|74h||02h
|-
|75h||1Fh
|-
|76h||00h
|-
|77h||00h
|-
|78h||00h
|-
|79h||00h
|-
|7Ah||00h
|-
|7Bh||00h
|-
|7Ch||00h
|-
|7Dh||00h
|-
|7Eh||00h
|-
|7Fh||00h
|}
|}

'''Interesting points:'''
* Flash is locked
* 4000h contains flash page 00h
* 8000h contains flash page 00h
* C000h contains ram page 00h
* The LCD driver is disconnected ([[83Plus:Ports:29|port 29]] causes this)
* The boot code is unlocked
* 84+BE/SE cannot be determined from [[83Plus:Ports:21|port 21]] as it reads 33h
* All parts of flash except privileged pages are non-executable (2C-2F, 3F, 6C-6F, and 7F)
* All of ram is non-executable except the first 1024 bytes of ram page 00h
* None of the LCD delay ports are set
* The clock is off
* The USB driver is off

==Memory Mapping==
Here's where the boot code gets fun. Since on boot all variables and ports have been reset, it would logically follow that execution should start at 0000h. There's a problem though, 0000h is always flash page 00h. In order to beat this, TI actually had to add a hack to put the boot code into the 0000h region.

* The calculator is in memory map mode 0
* Page 7Fh is swapped into the 0000h region and acts completely normal
* Every other port works exactly how it should
* Page 00h is restored to 0000h when and only when a byte is executed in a memory bank controlled by [[83Plus:Ports:06|port 06]]. This means that in memory map mode 0, a byte must be executed in the 4000h-7FFFh range, and in memory map mode 1, a byte must be executed in the 4000-BFFFh range. When this byte is executed, 00h instantly goes back to 0000h.

==Gathering this Information==
This information could only be gathered by replacing the boot code. This was a very dangerous operation as one mistake will brick the calculator. You should not attempt to recreate anything on this page or write your own boot code unless you are a master at z80 assembly.

← Older revision		Revision as of 21:03, 17 February 2012
Line 330:		Line 330:
	This information could only be gathered by replacing the boot code. This was a very dangerous operation as one mistake will brick the calculator. You should not attempt to recreate anything on this page or write your own boot code unless you are a master at z80 assembly.		This information could only be gathered by replacing the boot code. This was a very dangerous operation as one mistake will brick the calculator. You should not attempt to recreate anything on this page or write your own boot code unless you are a master at z80 assembly.

−	[[Category:83Plus:General Hardware Information]]	+	[[Category:83Plus:General Hardware Information\|State of the calculator at boot]]

← Older revision		Revision as of 16:51, 28 November 2011
Line 329:		Line 329:
	==Gathering this Information==		==Gathering this Information==
	This information could only be gathered by replacing the boot code. This was a very dangerous operation as one mistake will brick the calculator. You should not attempt to recreate anything on this page or write your own boot code unless you are a master at z80 assembly.		This information could only be gathered by replacing the boot code. This was a very dangerous operation as one mistake will brick the calculator. You should not attempt to recreate anything on this page or write your own boot code unless you are a master at z80 assembly.
		+
		+	[[Category:83Plus:General Hardware Information]]

@@ Line 319: / Line 319: @@
 * The calculator is in memory map mode 0
-* Page 7Fh is swapped into the 0000h region and acts completely normal
+* 0000h contains the boot code (3Fh / 7Fh) and behaves normally
-* Every other port works exactly how it should
+* 4000h contains flash page 00h
 * Page 00h is restored to 0000h when and only when a byte is executed in a memory bank controlled by [[83Plus:Ports:06|port 06]]. This means that in memory map mode 0, a byte must be executed in the 4000h-7FFFh range, and in memory map mode 1, a byte must be executed in the 4000-BFFFh range. When this byte is executed, 00h instantly goes back to 0000h.

@@ Line 322: / Line 322: @@
 * Every other port works exactly how it should
 * Page 00h is restored to 0000h when and only when a byte is executed in a memory bank controlled by [[83Plus:Ports:06|port 06]]. This means that in memory map mode 0, a byte must be executed in the 4000h-7FFFh range, and in memory map mode 1, a byte must be executed in the 4000-BFFFh range. When this byte is executed, 00h instantly goes back to 0000h.
 ==Gathering this Information==
 This information could only be gathered by replacing the boot code. This was a very dangerous operation as one mistake will brick the calculator. You should not attempt to recreate anything on this page or write your own boot code unless you are a master at z80 assembly.