C517A_99 Datasheet, PDF (93/218 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Bit
T2PS
T2PS1
T2R1
T2R0
T2I1
T2I0
ET2
EXEN2
EXF2
TF2
On-Chip Peripheral Components
C517A
Symbol
Timer 2 prescaler select bits
Based on f_OSC/12 these bits define the prescaler divider ratio of the timer 2
input clock according the following table.
T2PS1
0
0
1
1
T2PS
0
1
0
1
Timer 2 Input Clock
f_OSC ÷ 12
f_OSC ÷ 24
f_OSC ÷ 48
f_OSC ÷ 96
Timer 2 reload mode selection
T2R1
0
1
1
T2R0
X
0
1
Reload Mode
Reload disabled
Mode 0 : auto-reload upon timer 2 overflow (TF2)
Mode 1: reload upon falling edge at pin P1.5 / T2EX
Timer 2 input selection
T2I1
0
0
1
1
T2I0
0
1
0
1
Input Mode
No input selected : timer 2 stops
Timer function : input frequency see table above
Counter function : external input controlled by pin P1.7
/ T2
Gated timer function : input controlled by pin T2/P1.7
Timer 2 Interrupt Enable.
If ET2 = 0, the timer 2 interrupt is disabled.
Timer 2 external reload interrupt enable
If EXEN2 = 0, the timer 2 external reload interrupt is disabled.
The external reload function is not affected by EXEN2.
Timer 2 external reload flag
Set when a reload is caused by a negative transition on pin T2EX while
EXEN2 = 1. If ET2 in IEN0 is set (timer 2 interrupt enabled), EXF2 = 1 will
cause an interrupt. Can be used as an additional external interrupt when the
reload function is not used. EXF2 must be cleared by software.
Timer 2 overflow flag
Set by a timer 2 overflow and must be cleared by software. If the timer 2
interrupt is enabled, TF2 = 1 will cause an interrupt.
Semiconductor Group
6-27