Difference between revisions of "83Plus:Ports:20"
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This port is not available on the normal TI-83+. On the normal TI-83+ this port is a shadow of [[83Plus:Ports:00|Port 00h]]. | This port is not available on the normal TI-83+. On the normal TI-83+ this port is a shadow of [[83Plus:Ports:00|Port 00h]]. | ||
| − | This port can contain values of 2 and 3, but the difference in speed is negligible. Using the crystal timers I came to these | + | This port can contain values of 2 and 3, but the difference in speed is negligible. Using the crystal timers I came to these approximate values. |
{| width="30%" border="1" cellspacing="1" bgcolor="white" | {| width="30%" border="1" cellspacing="1" bgcolor="white" | ||
| width="40%" | Port Contents | | width="40%" | Port Contents | ||
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| width="60%" | ~14.990 mhz | | width="60%" | ~14.990 mhz | ||
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| − | I | + | I suggest still using 1 as the speed setting value since the total effect of the other values are not known. These modes are distinguished by LCD delaying hardware, ports 29-2C. |
Revision as of 06:11, 23 August 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. |
Contents
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.
This port can contain values of 2 and 3, but the difference in speed is negligible. Using the crystal timers I came to these approximate values.
| Port Contents | CPU Clock Speed |
| 00 | ~6.089 mhz |
| 01 | ~14.965 mhz |
| 02 | ~14.980 mhz |
| 03 | ~14.990 mhz |
I suggest still using 1 as the speed setting value since the total effect of the other values are not known. These modes are distinguished by LCD delaying hardware, ports 29-2C.
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, especially since both lines are high normally...
Credits and Contributions
- Michael Vincent: Documentation and his faster approach as found here.
