C868_02 Datasheet, PDF (59/244 Pages) Infineon Technologies AG – 8 - Bit CMOS Microcontroller

C868
On-Chip Peripheral Components
4.5.1.2 Mode 0
Putting either timer 0, 1 into mode 0 configures it as an 8-bit timer with a divide-by-32
prescaler. Figure 4-2 shows the mode 0 operation.
In this mode, the timer register is configured as a 13-bit register. As the count rolls over
from all 1’s to all 0’s, it sets the timer overflow flag TF0. The overflow flag TF0 then can
be used to request an interrupt. The counted input is enabled to the timer when TR0 = 1
and either Gate = 0 or INT0 = 1 (setting Gate = 1 allows the timer to be controlled by
external input INT0, to facilitate pulse width measurements). TR0 is a control bit in the
special function register TCON; Gate is in TMOD.
The 13-bit register consists of all 8 bits of TH0 and the lower 5 bits of TL0. The upper 3
bits of TL0 are indeterminate and should be ignored. Setting the run flag (TR0) does not
clear the registers.
Mode 0 operation is the same for timer 0 as for timer 1. Substitute TR0, TF0, TH0, TL0
and INT0 for the corresponding timer 1 signals in Figure 4-2. There are two different
gate bits, one for timer 1 (TMOD.7) and one for timer 0 (TMOD.3).
f_SYS 12
=1
Gate
INT0/INT1 ^Pin
C/T = 0
TR0
1
TL0 TH0
(5 Bits) (8 Bits)
TF0
Interrupt
Control
Figure 4-2 Timer 0, Mode 0: 13-Bit Timer
User’s Manual
4-15
V 0.4, 2002-01