A82: Interrupt speed
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A82: Interrupt speed
Hi,
Does anyone know the correct interrupt speed for the TI-82?
I made a little program and found out what you read below, any comments? The core of the program is a 26 T-states long loop run with the 4 different speed settings.
When I run it on my emulator with speed control (you'll get that version too soon) I get the values below.
The period is number of T-states between each interrupt and the number of T-states inside the interrupt routine is calculated. The differences are probably just measurement errors.
Period Loops Interrupt routine T-states
10000 365 510
20000 750 500
30000 1134 516
40000 1519 506
50000 1903 522
60000 2288 512
--> average interrupt routine T-states = 511
The speed (here in binary) is written to bits 1 & 2 of ports 4.
The old and new are two different set of batteries and the period is calculated.
Speed Old New Old period New period
00 441 457 11977 12393
01 1055 1092 27941 28903
10 1670 1729 43931 45465
11 2286 2364 59947 61975
This suggests a period of about 62000 T-states on fresh batteries.
Another interesting thing is that the period gets lower when the CPU runs slower. The blink rate of the cursor is probably constant no matter how bad batteries the calculator have.
If the calculator runs at 6 MHz and the interrupt period is 62500 there are 96 interrupts each second, which might be the magic value for fresh batteries - or?
Sincerely,
-/- David Eriksson -/-
CalcEm - The Calculator Emulator -> http://www.2goodsoft.com/calcem/