71M6521DE/71M6521FE
Energy Meter IC
DATASHEET
JANUARY 2008
Interrupt Request register (IRCON)
MSB
LSB
EX6
IEX5
IEX4
IEX3
IEX2
Table 44: The IRCON Register
Bit
Symbol Function
IRCON.7
IRCON.6
IRCON.5
IRCON.4
IRCON.3
IRCON.2
IRCON.1
IRCON.0
-
-
IEX6
IEX5
IEX4
IEX3
IEX2
-
External interrupt 6 edge flag
External interrupt 5 edge flag
External interrupt 4 edge flag
External interrupt 3 edge flag
External interrupt 2 edge flag
Table 45: The IRCON Bit Functions
Only TF0 and TF1 (timer 0 and timer 1 overflow flag) will be automatically cleared by hardware when the service
routine is called (Signals T0ACK and T1ACK – port ISR – active high when the service routine is called).
External Interrupts
The 71M6521DE/FE MPU allows seven external interrupts. These are connected as shown in Table 46. The direction of
interrupts 2 and 3 is programmable in the MPU. Interrupts 2 and 3 should be programmed for falling sensitivity. The generic
8051 MPU literature states that interrupt 4 through 6 are defined as rising edge sensitive. Thus, the hardware signals attached
to interrupts 5 and 6 are inverted to achieve the edge polarity shown in Table 46.
External
Interrupt
Connection
Digital I/O High Priority
Polarity
Flag Reset
0
1
2
3
4
5
6
see DIO_Rx
see DIO_Rx
falling
automatic
automatic
automatic
automatic
automatic
automatic
manual
Digital I/O Low Priority
FWCOL0, FWCOL1
CE_BUSY
falling
PLL_OK (rising), PLL_OK (falling)
EEPROM busy
rising
falling
XFER_BUSY OR RTC_1SEC
falling
Table 46: External MPU Interrupts
FWCOLx interrupts occur when the CE collides with a flash write attempt. See the flash write description for more detail.
SFR (special function register) enable bits must be set to permit any of these interrupts to occur. Likewise, each interrupt has
its own flag bit, which is set by the interrupt hardware, and reset by the MPU interrupt handler. Note that XFER_BUSY,
RTC_1SEC, FWCOL0, FWCOL1, PLLRISE, PLLFALL, have their own enable and flag bits in addition to the interrupt 6, 4, and
2 enable and flag bits.
IE0 through IEX6 are cleared automatically when the hardware vectors to the interrupt handler. The other flags, IE_XFER
through IE_PB, are cleared by writing a zero to them. Since these bits are in a bit-addressable SFR byte, common practice
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