C868_02 Datasheet, PDF (70/244 Pages) Infineon Technologies AG – 8 - Bit CMOS Microcontroller

C868
On-Chip Peripheral Components
f_SYS 12
C/T2 = 0
C/T2 = 1
TR2
Pin
T2
T2L/H
Overflow
OR
RC2L/H
TF2
Timer 2
OR
Interrupt
EXF2
Pin
T2EX
EXEN2
Figure 4-6 Auto-Reload Mode (DCEN = 0)
4.6.5.2 Up/Down Count Enabled
If DCEN=1, the up-down count selection is enabled. The direction of count is determined
by the level at input pin T2EX. The operational block diagram is shown in Figure 4-7.
A logic 1 at pin T2EX sets the timer/counter 2 to up counting mode. The timer/counter,
therefore, counts up to a maximum of FFFF_H. Upon overflow, bit TF2 is set and the timer/
counter registers are reloaded with a 16-bit reload of the RC2L/H registers. A fresh count
sequence is started and the timer counts up from this reload value as in the previous
count sequence. This reload value is chosen by software, prior to the occurrence of an
overflow condition.
A logic 0 at pin T2EX sets the timer/counter 2 to down counting mode. The timer/counter
counts down and underflows when the T2L/H value reaches the value stored at registers
User’s Manual
4-26
V 0.4, 2002-01