ST72F321J ST Microelectronics, ST72F321J Datasheet - Page 37

• Manufacturer Part Number: ST72F321J
• Description: 8-BIT MCU
• Manufacturer: ST Microelectronics

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DataSheet
7.7 EXTERNAL INTERRUPT CONTROL REGISTER (EICR)
Read /Write
Reset Value: 0000 0000 (00h)
Bit 7:6 = IS1[1:0] ei2 and ei3 sensitivity
The interrupt sensitivity, defined using the IS1[1:0]
bits, is applied to the following external interrupts:
- ei2 (port B3..0)
- ei3 (port B4)
These 2 bits can be written only when I1 and I0 of
the CC register are both set to 1 (level 3).
Bit 5 = IPB Interrupt polarity for port B
This bit is used to invert the sensitivity of the port B
[3:0] external interrupts. It can be set and cleared
by software only when I1 and I0 of the CC register
are both set to 1 (level 3).
0: No sensitivity inversion
1: Sensitivity inversion
IS11 IS10
IS11 IS10
IS11
0
0
1
1
0
0
1
1
7
4
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IS10
0
1
0
1
0
1
0
1
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Falling edge only
Rising edge only
IPB
Falling edge &
IPB bit =0
low level
External Interrupt Sensitivity
External Interrupt Sensitivity
IS21
Falling edge & low level
Rising and falling edge
Rising and falling edge
Falling edge only
Rising edge only
IS20
IPA
Falling edge only
Rising edge only
Rising edge
& high level
IPB bit =1
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0
0
0
Bit 4:3 = IS2[1:0] ei0 and ei1 sensitivity
The interrupt sensitivity, defined using the IS2[1:0]
bits, is applied to the following external interrupts:
- ei0 (port A3..0)
- ei1 (port F2..0)
These 2 bits can be written only when I1 and I0 of
the CC register are both set to 1 (level 3).
Bit 2 = IPA Interrupt polarity for port A
This bit is used to invert the sensitivity of the port A
[3:0] external interrupts. It can be set and cleared
by software only when I1 and I0 of the CC register
are both set to 1 (level 3).
0: No sensitivity inversion
1: Sensitivity inversion
Bits 1:0 = Reserved, must always be kept cleared.
IS21 IS20
IS21 IS20
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Falling edge only
Rising edge only
Falling edge &
IPA bit =0
low level
External Interrupt Sensitivity
External Interrupt Sensitivity
Falling edge & low level
Rising and falling edge
Rising and falling edge
Falling edge only
Rising edge only
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Falling edge only
Rising edge only
Rising edge
& high level
IPA bit =1
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