C509-L_97 Datasheet, PDF (146/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C509-L
6.3.4.6.2 Capture Function of Registers CC10 to CC17
The capture function is selected by programming the direction register related to port 9 (DIR9). With
the direction bit of DIR9 = 1 the capture function at the corresponding port 9 pin is selected. Each
of the eight compare/capture registers CC10 to CC17 can be used to latch the current 16-bit value
of the compare timer 1 registers by a positive or a negative transition at the corresponding port 9 pin.
The bits located in the SFR CAFR are used to define selectively, whether a positive or a negative
transition at a port 9 pin forces a capture event. CAFR is a mapped register.and can only be
accessed when bit RMAP in SFR SYSCON is set.
Special Function Register CAFR (Mapped Address F7H)
MSB
Bit No. 7
6
5
4
3
2
F7H
.7
.6
.5
.4
.3
.2
Reset Value : 00H
LSB
1
0
.1
.0 CAFR
Bit
CAFR.7-0
Function
Capture on falling / rising edge selection bits
CAFR.x = 0 : Capture into CC(10+x) on falling edge at pin P9.x is selected
(reset value)
CAFR.x = 1 : Capture into CC(10+x) on rising edge at pin P9.x is selected.)
The level at the corresponding port 9 pin is sampled every state within a machine cycle. For
example, with fosc = 16 MHz a state lasts for 62.5 ns. When the compare timer 1 input clock is
selected to fosc, the resulting resolution is 125 ns. The rise/fall time of the external capture signal
must be observed.
At a capture event with the CC10-CC17 register the corresponding interrupt request flag which is
located in SFR IRCON2 is set
Semiconductor Group
6-68
1997-10-01