71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
Interrupts
The 80515 provides 11 interrupt sources with four priority levels. Each source has its own request flag(s) located in a special
function register (TCON, IRCON, and SCON). Each interrupt requested by the corresponding flag can be individually enabled
or disabled by the enable bits in SFRs IEN0, IEN1, and IEN2.
External interrupts are the interrupts external to the 80515 core, i.e. signals that originate in other parts of the 71M6511/6511H,
for example the CE, DIO, RTC EEPROM interface, comparators.
Interrupt Overview: When an interrupt occurs, the MPU will vector to the predetermined address as shown in Table 51. Once
interrupt service has begun, it can be interrupted only by a higher priority interrupt. The interrupt service is terminated by a
return from instruction, "RETI". When a RETI instruction is performed, the processor will return to the instruction that would
have been next when the interrupt occurred.
When the interrupt condition occurs, the processor will also indicate this by setting a flag bit. This bit is set regardless of
whether the interrupt is enabled or disabled. Each interrupt flag is sampled once per machine cycle, then samples are polled
by the hardware. If the sample indicates a pending interrupt when the interrupt is enabled, then the interrupt request flag is set.
On the next instruction cycle, the interrupt will be acknowledged by hardware forcing an LCALL to the appropriate vector
address, if the following conditions are met:
•
•
•
No interrupt of equal or higher priority is already in progress.
An instruction is currently being executed and is not completed.
The instruction in progress is not RETI or any write access to the registers IEN0, IEN1, IEN2, IP0 or IP1.
Interrupt response will require a varying amount of time depending on the state of the MPU when the interrupt occurs. If the
MPU is performing an interrupt service with equal or greater priority, the new interrupt will not be invoked. In other cases, the
response time depends on the current instruction. The fastest possible response to an interrupt is 7 machine cycles. This
includes one machine cycle for detecting the interrupt and six cycles to perform the LCALL.
Special Function Registers for Interrupts:
Interrupt Enable 0 register (IE0)
MSB
LSB
EX0
EAL
WDT
ES0
ET1
EX1
ET0
Table 34: The IEN0 Register
Bit
Symbol
Function
IEN0.7
IEN0.6
IEN0.5
IEN0.4
IEN0.3
IEN0.2
IEN0.1
IEN0.0
EAL
WDT
-
ES0
ET1
EX1
ET0
EX0
EAL=0 – disable all interrupts
Not used for interrupt control
ES0=0 – disable serial channel 0 interrupt
ET1=0 – disable timer 1 overflow interrupt
EX1=0 – disable external interrupt 1
ET0=0 – disable timer 0 overflow interrupt
EX0=0 – disable external interrupt 0
Table 35: The IEN0 Bit Functions
Page: 29 of 95
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