Difference between revisions of "83Plus:Ports:05"
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== Synopsis == | == Synopsis == | ||
'''Port Number:''' 05h | '''Port Number:''' 05h | ||
Revision as of 09:45, 28 March 2005
Synopsis
Port Number: 05h
Function: RAM Paging Port
This port can be used to control what RAM page is paged into the C000h-FFFFh memory bank. Note that it can only page RAM pages (you can't do flash pages.) This port is only avalible on the 83+ Silver Edition and the 84+ Family (on the 83+ Black Edition, it does nothing.)
Read Values
Returns the current RAM page.
Write Values
Sets the current RAM page, by giving a value in 00h-07h, inclusive. When you work with the other paging ports, RAM pages are given in 80h-87h, but this port does not need bit 7 to be set. You cannot set the upper four bits.
Comments
The above only applies to the TI-83+ SE and the TI-84+. Port 5 on the standard TI-83+ has an unknown function related to the Flash execution protection on those calculators.
At least on my TI-84+, if you output a value with bit 3 set, reading from the port will return a value with bit 3 set. This would imply that you can use RAM pages 08h-0Fh, but these RAM pages do not exist--this bit is simply ignored (only bits 0-2 actually determine what RAM page is active.)
Credits and Contributions
- Michael Vincent: Initial documentation.
