C541U_99 Datasheet, PDF (154/192 Pages) Siemens Semiconductor Group – 8-BIT CMOS MICROCONTROLLER

Interrupt System
C541U
The edge-triggered interrupt mode selection for the external interrupts is selected by bits in SFR
ITCON (External Interrupt Trigger Condition Register). The edge-trigger mode selection is defined
in a way (default value of ITCON after reset), that their function is upward compatible to the basic
external interrupt functionality of the C501.
Special Function Registers ITCON (Address 9AH)
Reset Value : XXXX1010_B
Bit No. MSB
LSB
7
6
5
4
3
2
1
0
9AH
–
–
–
– I1ETF I1ETR I0ETF I0ETR ITCON
INT1
INT0
Bit
–
IxETF
IxETR
Function
Reserved bit for future use.
External Interrupt Edge Trigger Mode Selection
(x=0,1 refers to INT0, INT1)
IxETF IxETR Function
0
0
INTx inputs are not sensitive for either rising or falling edge
0
1
INTx operates in rising edge-triggered mode
1
0
INTx operates in falling edge-triggered mode
(default after reset)
1
1
INTx operates in falling and rising edge-triggered mode
Semiconductor Group
7-21
1997-10-01