SAB80515 Datasheet, PDF (85/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

On-Chip Peripheral Components
Table 7-9
Additional Special Function Registers of Timer 2
Symbol
CCEN
CCH1
CCH2
CCH3
CCL1
CCL2
CCL3
CRCH
CRCL
IRCON
TH2
TL2
T2CON
Description
Comp./capture enable reg.
Comp./capture reg. 1, high byte
Comp./capture reg. 2, high byte
Comp./capture reg. 3, high byte
Comp./capture reg. 1, low byte
Comp./capture reg. 2, low byte
Comp./capture reg. 3, low byte
Com./rel./capt. reg., high byte
Com./rel./capt. reg., low byte
Interrupt control register
Timer 2, high byte
Timer 2, low byte
Timer 2 control register
Address
0C1H
0C3H
0C5H
0C7H
0C2H
0C4H
0C6H
0CBH
0CAH
0C0H
0CDH
0CCH
0C8H
7.5.1 Timer 2
The timer 2, which is a 16-bit-wide register, can operate as timer, event counter, or gated timer.
Timer Mode
In timer function, the count rate is derived from the oscillator frequency. A 2:1 prescaler offers the
possibility of selecting a count rate of 1/12 or 1/24 of the oscillator frequency. Thus, the 16-bit timer
register (consisting of TH2 and TL2) is either incremented in every machine cycle or in every second
machine cycle. The prescaler is selected by bit T2PS in special function register T2CON (see
figure 7-35). lf T2PS is cleared, the input frequency is 1/12 of the oscillator frequency; if T2PS is
set, the 2:1 prescaler gates 1/24 of the oscillator frequency to the timer.
Gated Timer Mode
In gated timer function, the external input pin T2 (P1.7) functions as a gate to the input of timer 2. lf
T2 is high, the internal clock input is gated to the timer. T2 = 0 stops the counting procedure. This
will facilitate pulse width measurements. The external gate signal is sampled once every machine
cycle (for the exact port timing, please refer to section 7.1 "Parallel I/O").
Semiconductor Group
85