XC886/888CLM
Interrupt System
User’s Manual
5-21
V1.3, 2010-02
Interrupt System, V 1.0
5.6.2
External Interrupt Control Registers
The seven external interrupts, EXT_INT[6:0], are driven into the XC886/888 from the
ports. External interrupts can be positive, negative, or double edge triggered. Registers
EXICON0 and EXICON1 specify the active edge for the external interrupt. Among the
external interrupts, external interrupt 0 and external interrupt 1 can be selected to bypass
edge detection for direct feed-through to the core. This signal to the core can be further
programmed to either low-level or negative transition activated, by the bits IT0 and IT1
in the TCON register. In addition to the corresponding interrupt node enable, each
external interrupt 2 to 6 may be disabled individually.
If the external interrupt is positive (negative) edge triggered, the external source must
hold the request pin low (high) for at least one CCLK cycle, and then hold it high (low)
for at least one CCLK cycle to ensure that the transition is recognized. If edge detection
is bypassed for external interrupt 0 and external interrupt 1, the external source must
hold the request pin “high” or “low” for at least two CCLK cycles.
External interrupts 0, 1, 2 and 6 support alternative input pin, selected via EXINTxIS bits
in SFRs MODPISEL and MODPISEL1. When switching inputs, the active edge/level
trigger select and the level on the associated pins should be considered to prevent
unintentional interrupt generation.
EXICON0
External Interrupt Control Register 0
Reset Value: F0
H
7
6
5
4
3
2
1
0
EXINT3
EXINT2
EXINT1
EXINT0
rw
rw
rw
rw
Field
Bits
Type Description
EXINT0
[1:0]
rw
External Interrupt 0 Trigger Select
00
Interrupt on falling edge
01
Interrupt on rising edge
10
Interrupt on both rising and falling edges
11
Bypass the edge detection. The interrupt
request signal directly feeds to the core.
EXINT1
[3:2]
rw
External Interrupt 1 Trigger Select
00
Interrupt on falling edge
01
Interrupt on rising edge
10
Interrupt on both rising and falling edges
11
Bypass the edge detection.The interrupt
request signal directly feeds to the core.
*
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