SDA6000 Datasheet, PDF (156/380 Pages) Infineon Technologies AG – Teletext Decoder with Embedded 16-bit Controller

SDA 6000
Peripherals
Run Control
The timer can be started or stopped by software through bit T3R (Timer T3 Run Bit).
Setting bit T3R will start the timer, clearing T3R stops the timer.
In gated timer mode, the timer will only run if T3R is set and the gate is active (high or
low, as programmed).
Note: When bit T2RC/T4RC in timer control register T2CON/T4CON is set, T3R will also
control (start and stop) auxiliary timer T2/T4.
Count Direction Control
The count direction of the core timer can either be controlled by software or by the
external input line T3EUD (Timer T3 External Up/Down Control Input). These options are
selected by bits T3UD and T3UDE in control register T3CON. When the up/down control
is executed by software (bit T3UDE = ‘0’), the count direction can be altered by setting
or clearing bit T3UD. When T3UDE = ‘1’, line T3EUD is selected to be the controlling
source of the count direction. However, bit T3UD can still be used to reverse the actual
count direction, as shown in the table below. If T3UD = ‘0’ and line T3EUD shows a low
level, the timer is counting up. With a high level T3EUD, the timer is counting down. If
T3UD = ‘1’, a high level at line T3EUD specifies counting up, and a low level specifies
counting down. The count direction can be changed regardless of whether the timer is
running or not.
When line T3EUD is used as external count direction control input, its associated port
pin must be configured as input.
Table 7-1 Core Timer T3 Count Direction Control
Line T3EUD Bit T3UDE Bit T3UD Count Direction
X
0
0
Count Up
X
0
1
Count Down
0
1
0
Count Up
1
1
0
Count Down
0
1
1
Count Down
1
1
1
Count Up
Note: The direction control works in the same way for core timer T3 and for auxiliary
timers T2 and T4. Therefore the lines and bits are named Tx …
Timer 3 Overflow/Underflow Monitoring
An overflow or underflow of timer T3 will clock the overflow toggle latch T3OTL in control
register T3CON. T3OTL can also be set or reset by software. Bit T3OE (Overflow/
Users Manual
7-5
2000-06-15