Clocking the 2068

Our 2068’s have a built-in clock, sometimes called the Frame counter. This clock starts at zero every time the computer is turned on. It increments the value at the variable address 23672 every 1/60th of a second until it reaches 255. This takes about 4 1/4 seconds and then resets to zero and increments the value at 23673. This counter will also go up to 255 but only every 18 minutes. At that time it, in turn, increments the final counter at address 23674. The final counter reaches 255 after about 3 days and 6 hours.

The counters can be reset to zero or any other value by POKEing the number into three addresses. The accuracy of the clock is .01 percent (+/- 10 seconds per day). The clock counts up as long as the 2068 is left on, with three exceptions:

• During a BEEP,
• During tape operations (SAVEing and LOADing),
• During printing on the printer.

Under the above three conditions, time will stand still and continue when the condition is completed. The following expression gives the present count on the clock:

 (65536*PEEK 23674+256*PEEK 23673+PEEK 23672)/60

When using this expression in a program it is possible to PEEK 23673 just as 23672 resets to zero. This will give a false reading of 23673 because it should have been incremented at that moment, between reading the two addresses. To overcome this situation, use the above expression twice successively, and take the highest reading.