Difference between revisions of "83Plus:Ports:21"
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| − | [[Category:83Plus:Ports:By_Address|21 - Hardware Type]] [[Category:83Plus:Ports: | + | [[Category:83Plus:Ports:By_Address:Protected|21 - Hardware Type]] [[Category:83Plus:Ports:By_Address|21 - Hardware Type]] [[Category:83Plus:Ports:By_Name|Hardware Type]] |
== Synopsis == | == Synopsis == | ||
'''Port Number:''' 21h | '''Port Number:''' 21h | ||
Revision as of 22:20, 29 March 2005
Synopsis
Port Number: 21h
Function: Hardware Type
This port is simply a protected register which is set by the boot code according to the hardware version.
Read Values
- Bit 0: 1 on either the 83+ SE or the 84+ SE, 0 on the 84+ basic.
- Bit 1: Unknown -- always set to zero
- Bits 2-7 do not seem to do anything.
Write Values
- [00h - FFh]: New value for the register
Comments
This port does not exist on the standard 83+. See port 2.
There is no reason to write to this port, but by reading from it you can determine something about the HW version.
TIOS polls both bits 0 and 1, by taking the logical AND with 3.
Example
in a,(2) ld b,a and 80h jr z,TI83p_BE in a,(21h) and 3 jr z,TI84p_BE bit 5,b jr z,TI83p_SE ; calculator is an 84+ SE TI84p_BE: ; calculator is an 84+ BE TI83p_SE: ; calculator is an 83+ SE TI83p_BE: ; calculator is an 83+ BE
