83Plus:Ports:2E

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 06.

Synopsis

Port Number: 2Eh

Function: CPU Speed Adjustment

Bits 4 and 5 can adjust the CPU speed to a certain degree. In order for the speed adjustment to work bit 1 must be set in the appropriate LCD Delay port according to the contents of port 20. In other words, if you wish to adjust the speed at 6mhz you must set bit 1 of port 29. Other bits of this port 2E may affect the speed but nothing significant. The default value for this port is 45h on the TI-84 Plus Silver Edition and 44h on the TI-83 Plus Silver Edition.

Read Values (bits 5-4)

• 00: The CPU is running at normal speed (100%)
• 01: The CPU is running at ~90% of normal speed
• 10: The CPU is running at ~95% of normal speed
• 11: The CPU is running at ~86% of normal speed

Write Values (bits 5-4)

• 00: Set the CPU to run at 100% of normal speed
• 01: Set the CPU to run at ~90% of normal speed
• 10: Set the CPU to run at ~95% of normal speed
• 11: Set the CPU to run at ~86% of normal speed

Comments

This port is not available on the normal TI-83+. On the normal TI-83+ this port is a shadow of Port 06h.

Example

ld a,0
out (20h),a    ;would be 6mhz
in a,(29h)
or 2           ;set bit 1
out (29h),a
ld a,74h       ;Set the CPU to ~5.1 MHz
out (2Eh),a

Credits and Contributions

• Michael Vincent: Documentation found here.