83Plus:Ports:0E - Revision history

Dr. D'nar at 04:28, 20 February 2013

2013-02-20T04:28:17Z

Dr. D'nar at 04:25, 20 February 2013

2013-02-20T04:25:18Z

Dr. D'nar: TI-84+CSE

2013-02-20T04:22:41Z

TI-84+CSE

Thepenguin77 at 02:18, 26 November 2011

2011-11-26T02:18:01Z

Thepenguin77: Created page with '0E-0F - Boot Code Paging Boot Code Paging == Synopsis == '''Port Numbers:''' 0Eh and 0Fh '''Function:''' …'

2011-11-26T00:45:15Z

Created page with '0E-0F - Boot Code Paging Boot Code Paging == Synopsis == '''Port Numbers:''' 0Eh and 0Fh '''Function:''' …'

New page

[[Category:83Plus:Ports:By_Address|0E-0F - Boot Code Paging]] [[Category:83Plus:Ports:By_Name|Boot Code Paging]]

== Synopsis ==
'''Port Numbers:''' 0Eh and 0Fh

'''Function:''' Boot Code Paging

These ports have no function on the 84+ line. They probably do something on the 83+ line.

=== Read Values ===
* Bits 0-1: Whatever was last written
* Bits 2-7: always 0

=== Write Values ===
* Bits 0-1: Set a new value
* Bit 2-7: No effect

== Comments ==
These two ports are written to very early in the boot code where they both receive 03 then 00. Port 0E is written to first and is used before accessing page 7F in the 8000h region via memory map mode 1. Port 0Fh is written to second before accessing page 7F in the 4000h region via memory map mode 0. Once execution is running normally in the 4000h region, both ports are set back to 00.

It would seem that port 0E is related to the 8000h range and port 0F is related to the 4000h range, but that might not be correct.

It has also been confirmed on all three ASIC revisions that this port is not necessary to fix the boot code memory mapping. For more information on that see: [[83Plus:State_of_the_calculator_at_boot|State of the calculator at boot]]

← Older revision		Revision as of 04:28, 20 February 2013
Line 6:		Line 6:
	'''Function:''' This port contains the high two bits of addresses for memory mapped in [[83Plus:Ports:06\|port 6]]. [[83Plus:Ports:0F\|Port 0F]] is an identical port that works with [[83Plus:Ports:07\|port 7]].		'''Function:''' This port contains the high two bits of addresses for memory mapped in [[83Plus:Ports:06\|port 6]]. [[83Plus:Ports:0F\|Port 0F]] is an identical port that works with [[83Plus:Ports:07\|port 7]].

		+	See also [[83Plus:Memory Mapping\|Memory Mapping]].

	=== Read Values ===		=== Read Values ===

@@ Line 2: / Line 2: @@
 == Synopsis ==
-'''Port Numbers:''' 0Eh
+'''Port Numbers:''' 0Eh and 0Fh
 '''Function:''' This port contains the high two bits of addresses for memory mapped in [[83Plus:Ports:06|port 6]]. [[83Plus:Ports:0F|Port 0F]] is an identical port that works with [[83Plus:Ports:07|port 7]].

@@ Line 1: / Line 1: @@
-[[Category:83Plus:Ports:By_Address|0E-0F - Boot Code Paging]] [[Category:83Plus:Ports:By_Name|Boot Code Paging]]
+[[Category:83Plus:Ports:By_Address|0E - MemA High Flash Address]] [[Category:83Plus:Ports:By_Name|MemA High Flash Address]]
 == Synopsis ==
-'''Port Numbers:''' 0Eh and 0Fh
+'''Port Numbers:''' 0Eh
-'''Function:''' Boot Code Paging
+'''Function:''' This port contains the high two bits of addresses for memory mapped in [[83Plus:Ports:06|port 6]]. [[83Plus:Ports:0F|Port 0F]] is an identical port that works with [[83Plus:Ports:07|port 7]].
 === Read Values ===
@@ Line 17: / Line 16: @@
 == Comments ==
-These two ports are written to very early in the boot code where they both receive 03 then 00. Port 0E is written to first and is used before accessing page 7F in the 8000h region via memory map mode 1. Port 0Fh is written to second before accessing page 7F in the 4000h region via memory map mode 0. Once execution is running normally in the 4000h region, both ports are set back to 00.
+These two ports are only useful for calculators with 4 or 8 MB of flash, namely, the TI-84+CSE. On 1 or 2 MB calculators, the values are ignored. The boot code of all models likes to write 03 to these ports early in the boot process, in order to ensure that the highest possible flash pages are swapped in. Of course, that only actually matters on the TI-84+CSE. On the TI-83+SE, TI-84+, and TI-84+SE, the value of these ports are ignored.
-It would seem that port 0E is related to the 8000h range and port 0F is related to the 4000h range, but that might not be correct.
+TI likes to write 00 to these ports before swapping RAM. However, that appears to be fully unnecessary; setting bit 7 of 06 or 07 correctly maps RAM into MemA or MemB without regard for the value of these ports.
-−
-It has also been confirmed on all three ASIC revisions that this port is not necessary to fix the boot code memory mapping. For more information on that see: [[83Plus:State_of_the_calculator_at_boot|State of the calculator at boot]]

@@ Line 6: / Line 6: @@
 '''Function:''' Boot Code Paging
-These ports have no function on the 84+ line. They probably do something on the 83+ line.
+These ports have no function on the 84+ line. They might do something on the 83+SE.
 === Read Values ===