SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 100

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

7.5.2
This timer - the fourth timer in the SAB 80C517 - is implemented to function as a fast 16-bit time
base for the compare registers CM0 to CM7. The compare timer combine with the CMx registers
can be employed as high-speed output unit or as a fast 16-bit pulse-width modulator unit. For this
case, every CMx register assigned to the compare timer automatically operates in compare
mode 0: a compare timer overflow sets the corresponding output line at port 4 to low level, a
compare match pulls the pin high again (see also section 7.5.4.1).
The minimum resolution attainable at the port 4 outputs is
The compare timer is provided with a 16-bit auto-reload and an 8-bit prescaler for a very high
flexibility concerning timer period length and input clock frequency. A block diagram of the compare
timer is shown in figure 7-36.
Input Clock Selection
The compare timer receives its input clock from a programmable prescaler which provides eight
different input frequencies:
selection can be done in a three-bit field (binary coded) in special function register CTCON (see
figure 7-37). Register CTCON can be written to at any time, its default value after reset is 00 H (that
is
Figure 7-36
Compare Timer Block Diagram
Semiconductor Group
f
OSC
/2 input frequency).
The Compare Timer
f
OSC
/2,
f
OSC
/4,
f
OSC
/8,
101
f
OSC
/16,
On-Chip Peripheral Components
t
CYCLE
f
OSC
/32,
/6 (appr. 166.6 ns at
f
OSC
/64,
f
OSC
/128,
f
OSC
f
OSC
= 12 MHz).
/256. The