Difference between revisions of "83Plus:Ports:20"

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[[Category:83Plus:Ports:By Address|20 - CPU Speed Port]] [[Category:83Plus:Ports:By Name|CPU Speed Port]]
 
[[Category:83Plus:Ports:By Address|20 - CPU Speed Port]] [[Category:83Plus:Ports:By Name|CPU Speed Port]]
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{{SE-Only Port|00}}
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== Synopsis ==
 
== Synopsis ==
 
'''Port Number:''' 20h
 
'''Port Number:''' 20h
  
 
'''Function:''' CPU Speed Port
 
'''Function:''' CPU Speed Port
 
'''Not present on the TI-83+ Basic!'''
 
  
 
This port controls the calculator's CPU speed. The CPU can be set to run at either 6MHz or 15MHz with this port.
 
This port controls the calculator's CPU speed. The CPU can be set to run at either 6MHz or 15MHz with this port.

Revision as of 13:59, 30 March 2005

This port only exists as a distinct port on the TI-83 Plus Silver Edition, the TI-84 Plus, and the TI-84 Plus Silver Edition. On the standard TI-83 Plus, it acts as a shadow of port 00.

Synopsis

Port Number: 20h

Function: CPU Speed Port

This port controls the calculator's CPU speed. The CPU can be set to run at either 6MHz or 15MHz with this port.

Read Values

  • 00h : The CPU is running at 6MHz.
  • 01h: THe CPU is running at 15MHz.

Write Values

  • 00h : Set the CPU to 6MHz.
  • 01h: Set the CPU to 15MHz.

Comments

This port is not available on the normal TI-83+. On the normal TI-83+ this port is a shadow of Port 00h.

Example

 in a, (2)
 and 80h
 jp z, NoCPUGoverner
 rlca ;Move the 1 bit in bit 7 to bit 0 (80h -> 01h)
 out (20h), a
NoCPUGoverner:

Michael Vincent documented another method to set the CPU speed (which is probably faster than my example).

in a, (2)
 rla
 sbc a, a
 out (20h), a

The only side effect of this is that on the TI-83+ Basic this will cause both linkport lines to go high - which shouldn't matter too much if you're not using the linkport at that time, especailly since both lines are high normally...

Credits and Contributions

  • Michael Vincent: Documentation and his faster approach as found here.