C515A_9708 Datasheet, PDF (76/182 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C515A
The T2CON timer 2 control register is a bitaddressable register which controls the timer 2 function
and the compare mode of registers CRC, CC1 to CC3.
Special Function Register T2CON (Address C8H)
Bit No.
C8H
MSB
7
CFH
T2PS
6
CEH
I3FR
5
CDH
I2FR
4
CCH
T2R1
3
CBH
T2R0
2
CAH
T2CM
1
C9H
T2I1
Reset Value : 00H
LSB
0
C8H
T2I0
T2CON
The shaded bit is not used in controlling timer/counter 2.
Bit
T2PS
I3FR
T2R1
T2R0
T2CM
T2I1
T2I0
Function
Prescaler select bit
When set, timer 2 is clocked in the “timer“ or “gated timer“ function with 1/24 of the
oscillator frequency. When cleared, timer 2 is clocked with 1/12 of the oscillator
frequency. T2PS must be 0 for the counter operation of timer 2.
External interrupt 3 falling/rising edge flag
Used for capture function in combination with register CRC. lf set, a capture to
register CRC (if enabled) will occur on a positive transition at pin P1.0 / INT3 / CC0.
lf I3FR is cleared, a capture will occur on a negative transition.
Timer 2 reload mode selection
T2R1
0
1
1
T2R0
X
0
1
Function
Reload disabled
Mode 0 : auto-reload upon timer 2 overflow (TF2)
Mode 1 : reload on falling edge at pin P1.5 / T2EX.
Compare mode bit for registers CRC, CC1 through CC3
When set, compare mode 1 is selected. T2CM = 0 selects compare mode 0.
Timer 2 input selection
T2I1
0
0
1
1
T2I0
0
1
0
1
Function
No input selected, timer 2 stops
Timer function :
input frequency = f_osc/12 (T2PS = 0) or f_osc/24 (T2PS = 1)
Counter function : external input signal at pin P1.7 / T2
Gated timer function : input controlled by pin P1.7 / T2
Semiconductor Group
6-25
1997-08-01