SAB80515 Datasheet, PDF (71/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

On-Chip Peripheral Components
7.3.4 Mode 3
Mode 3 has different effects on timer 0 and timer 1. Timer 1 in mode 3 simply holds its count. The
effect is the same as setting TR1 = 0. Timer 0 in mode 3 establishes TL0 and TH0 as two separate
counters. The logic for mode 3 on timer 0 is shown in figure 7-24. TL0 uses the timer 0 control bits:
C/T, GATE, TR0, INT0, and TF0. TH0 is locked into a timer function (counting machine cycles) and
takes over the use of TR1 and TF1 from timer 1. Thus, TH0 now controls the "timer 1" interrupt.
Mode 3 is provided for applications requiring an extra 8-bit timer or counter. When timer 0 is in
mode 3, timer 1 can be turned on and off by switching it out of and into its own mode 3, or can still
be used by the serial channel as a baud rate generator, or in fact, in any application not requiring
an interrupt from timer 1 itself.
Figure 7-24
Timer/Counter 0, Mode 3: Two 8-Bit Timers/Counters
Semiconductor Group
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