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Rev. 1.00
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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Interrupts
Interrupts
How byte of Interrupt Priority Register 3: IP3H
SFR Address: CFh
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
PTBH
PADCH
PI�CH
PSPIH
R/W
—
—
—
—
R/W
R/W
R/W
R/W
POR
—
—
—
—
0
0
0
0
Bit 7~4
Unimplemented, read as “0”
Bit 3
PTBH:
Time Base Interrupt Priority high
High order bit for Time Base Interrupt Priority level.
Bit 2
PADCH:
ADC Interrupt priority high
High order bit for ADC interrupt priority level.
Bit 1
PI2CH:
I
2
C Interrupt priority high
High order bit for I
2
C interrupt priority level.
Bit 0
PSPIH:
SPI Interrupt priority high
High order bit for SPI interrupt priority level.
External Interrupt
The external interrupt pins are pin-shared with the I/O pins and can be configured as an external
interrupt pin if the corresponding external interrupt enable bits in the interrupt control registers
have been set. The pin must also be setup as an input by setting the corresponding bits in the
port mode register. Any pull-high resistor settings will also remain valid when the pin is used as
an external interrupt pin. When the interrupt is enabled, the stack is not full and a falling edge,
a rising edge or a high to low level transition appears on the external interrupt pin, a subroutine
call to the external interrupt vector, will take place. When the interrupt is serviced, the external
interrupt request flag will be automatically reset and the EAL bit must be cleared by the application
program to disable other interrupts.
The IT0, IT1, I2FR and I3FR bits are used to select the type of active edge that will trigger the
external interrupt for INT0, INT1, INT2 and INT3 respectively. The other external interrupts,
INT4, INT5 and INT6, are triggered with a rising edge signal.
External Interrupt Trigger Type
Ext Int
Trigger Type
Register
Bit
INT0
Falling Edge o� Low Level
TCON
IT0
INT1
Falling Edge o� Low Level
TCON
IT1
INT�
Falling Edge o� Rising Edge
T�CON
I�FR
INT3
Falling Edge o� Rising Edge
T�CON
I3FR
INT4
Rising Edge
—
—
INT�
Rising Edge
—
—
INT6
Rising Edge
—
—