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C161U
Interrupt and Trap Functions
Data Sheet
127
2001-04-19
Note:
The non-maskable interrupt input pin NMI and the reset input RSTIN provide
another possibility for the CPU to react on an external input signal. NMI and RSTIN
are dedicated input pins, which cause hardware traps.
7.8.1
Fast External Interrupts
The input pins that may be used for external interrupts are sampled every 16 TCL, ie.
external events are scanned and detected in timeframes of 16 TCL. C161U provides 2
external interrupt inputs that are sampled every 2 TCL, so external events are captured
faster than with standard interrupt inputs.
The pins of Port 2 (P2.1...P2.0) can individually be programmed to this fast interrupt
mode, where also the trigger transition (rising, falling or both) can be selected. The
External Interrupt Control register EXICON controls this feature for all 8 pins.
EXICON (F1C0
H
/ E0
H
)
15
14
ESFR
8
Reset Value: 0000
H
3
2
Note:
1. Although the C161U provides only two pins of Port 2 which can be used for fast
external interrupts, bit fields EXI7ES..EXI2ES must be set in order to use alternate
sources as fast external interrupts. For alternate sources, refer to register EXISEL on
page 128.
2. The fast external interrupt inputs are sampled every 2 TCL. The interrupt request
arbitration and processing, however, is executed every 8 TCL.
3. In Sleep mode, no clock is available. Therefore sampling is performed with
asynchronous structures.
4. In Sleep mode fast external interrupts as well as the NMI input are controlled for spike
suppression in the System Control Block. Input signals shorter than 10 ns are
suppressed, detection is guaranteed for minimum 150 ns input signals.
Bit
EXIxES
Function
External Interrupt x Edge Selection Field (x=7...0)
0 0: Fast external interrupts disabled: standard mode
0 1: Interrupt on positive edge (rising)
1 0: Interrupt on negative edge (falling)
1 1: Interrupt on any edge (rising or falling)
5
4
1
0
11
10
9
7
6
13
12
rw
rw
rw
EXI2ES
EXI0ES
EXI1ES
rw
rw
rw
EXI7ES
EXI5ES
EXI6ES
rw
rw
EXI3ES
EXI4ES