[stella] Timer Test, Take 1

[seagtgruff at aol.com]

Okay, here's my first version of a timer test. Right now it doesn't test the timer interrupt flag, just the countdown behavior before and after passing 0 the first time.

You can select which timer interval you want to test. Then it sets the timer to 5, and detects which cycles the timer changes to 4, 3, 2, 1, 0, 255 ($FF), 254 ($FE), 253 ($FD), 252 ($FC), and 251 ($FB).

Scroll up and down with the joystick on the first screen to pick an interval, then press the fire button to begin the detection process.

When the second screen comes up, scroll up and down to highlight one of the values, and the cycle on which the timer changes to that value will be shown in the score at the bottom. If the score is green, then it matches the expected result; if it's red, then it disagrees with the expected result.

Cycle 0 is the last cycle of the store instruction which sets the timer, so cycle 1 is the first cycle after the timer has been set. Stella 2.5 fails for $FE, $FD, $FC, and $FB, but Stella 2.5.1 and z26 are correct.

Press the fire button again to return to the first screen so you can choose another timer interval.

Michael
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