71M6533 Datasheet, PDF (33/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

FDS_6533_6534_004
71M6533/G/H and 71M6534/H Data Sheet
External MPU Interrupts
The seven external interrupts are the interrupts external to the 80515 core, i.e. signals that originate in
other parts of the 71M6533/71M6534, for example the CE, DIO, RTC, EEPROM interface.
The external interrupts are connected as shown in Table 30. The polarity of interrupts 2 and 3 is
programmable in the MPU via the I3FR and I2FR bits in T2CON. Interrupts 2 and 3 should be programmed
for falling sensitivity (I3FR = I2FR = 0). The generic 8051 MPU literature states that interrupts 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 30.
Table 30: External MPU Interrupts
External
Interrupt
0
1
2
3
4
5
6
Connection
Polarity
Digital I/O High Priority
Digital I/O Low Priority
FWCOL0, FWCOL1, SPI
CE_BUSY
PLL_OK (rising), PLL_OK (falling)
EEPROM busy
XFER_BUSY, RTC_1SEC or WD_NROVF
see Section 1.5.7
see Section 1.5.7
falling
falling
rising
falling
falling
Flag Reset
automatic
automatic
automatic
automatic
automatic
automatic
manual
External interrupt 0 and 1 can be mapped to pins on the device using DIO resource maps. See Section
1.5.7 Digital I/O for more information.
FWCOLx interrupts occur when the CE collides with a flash write attempt. See the flash write description
in the Flash Memory section for more detail.
SFR 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. XFER_BUSY,
RTC_1SEC, WD_NROVF, FWCOL0, FWCOL1, SPI, PLLRISE and PLLFALL have their own enable and
flag bits in addition to the interrupt 6, 4 and enable and flag bits (see Table 31).
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 an SFR bit addressable byte, common practice would be to clear them
with a bit operation, but this must be avoided. The hardware implements bit operations as a
byte wide read-modify-write hardware macro. If an interrupt occurs after the read, but before
the write, its flag will be cleared unintentionally.
The proper way to clear the flag bits is to write a byte mask consisting of all ones except for a
zero in the location of the bit to be cleared. The flag bits are configured in hardware to ignore
ones written to them.
Table 31: Interrupt Enable and Flag Bits
Interrupt Enable
Name
Location
EX0
SFR A8[0]
EX1
SFR A8[2]
EX2
SFR B8[1]
EX3
SFR B8[2]
EX4
SFR B8[3]
EX5
SFR B8[4]
EX6
SFR B8[5]
Interrupt Flag
Name
Location
IE0
SFR 88[1]
IE1
SFR 88[3]
IEX2
SFR C0[1]
IEX3
SFR C0[2]
IEX4
SFR C0[3]
IEX5
SFR C0[4]
IEX6
SFR C0[5]
Interrupt Description
External interrupt 0
External interrupt 1
External interrupt 2
External interrupt 3
External interrupt 4
External interrupt 5
External interrupt 6
Rev 2
33