UPSD3422_06 Datasheet, PDF (92/293 Pages) STMicroelectronics – Turbo Plus Series Fast Turbo 8032 MCU with USB and Programmable Logic

Standard 8032 timer/counters
uPSD34xx
20.6.1
20.6.2
Note:
Capture mode
In Capture Mode there are two options which are selected by the bit EXEN2 in T2CON.
Figure 28 on page 97 illustrates Capture mode.
If EXEN2 = 0, then Timer 2 is a 16-bit timer if C/T2 = 0, or it is a 16-bit counter if C/T2 = 1,
either of which sets the interrupt flag bit TF2 upon overflow.
If EXEN2 = 1, then Timer 2 still does the above, but with the added feature that a 1-to-0
transition at external input pin T2X causes the current value in the Timer 2 registers, TL2
and TH2, to be captured into Registers RCAP2L and RCAP2H, respectively. In addition, the
transition at T2X causes interrupt flag bit EXF2 in T2CON to be set. Either flag TF2 or EXF2
will generate an interrupt and the MCU must read both flags to determine the cause. Flags
TF2 and EXF2 are not automatically cleared by hardware, so the firmware servicing the
interrupt must clear the flag(s) upon exit of the interrupt service routine.
Auto-reload mode
In the Auto-reload Mode, there are again two options, which are selected by the bit EXEN2
in T2CON. Figure 29 on page 97 shows Auto-reload mode.
If EXEN2 = 0, then when Timer 2 counts up and rolls over from FFFFh it not only sets the
interrupt flag TF2, but also causes the Timer 2 registers to be reloaded with the 16-bit value
contained in Registers RCAP2L and RCAP2H, which are preset with firmware.
If EXEN2 = 1, then Timer 2 still does the above, but with the added feature that a 1-to-0
transition at external input T2X will also trigger the 16-bit reload and set the interrupt flag
EXF2. Again, firmware servicing the interrupt must read both TF2 and EXF2 to determine
the cause, and clear the flag(s) upon exit.
The uPSD34xx does not support selectable up/down counting in Auto-reload mode (this
feature was an extension to the original 8032 architecture).
92/293