ADE5166_08 AD [Analog Devices], ADE5166_08 Datasheet - Page 89

• Manufacturer Part Number: ADE5166_08
• Description: Single-Phase Energy Measurement IC with 8052 MCU, RTC, and LCD Driver
• Manufacturer: AD [Analog Devices]

INTERRUPT VECTORS
When an interrupt occurs, the program counter is pushed onto the
stack, and the corresponding interrupt vector address is loaded
into the program counter. When the interrupt service routine is
complete, the program counter is popped off the stack by a RETI
instruction. This allows program execution to resume from where
it was interrupted. The interrupt vector addresses are shown in
Table 86.
Table 86. Interrupt Vector Addresses
Source
IE0
TF0
IE1
TF1
RI + TI
TF2 + EXF2
ITEMP (Temperature ADC)
ISPI/I2CI
IPSM (Power Supply)
IADE (Energy Measurement DSP)
IRTC (RTC Interval Timer)
WDT (Watchdog Timer)
RI2 + TI2
INTERRUPT LATENCY
The 8052 architecture requires that at least one instruction
execute between interrupts. To ensure this, the 8052 MCU
core hardware prevents the program counter from jumping to
an ISR immediately after completing a RETI instruction or an
access of the IP and IE SFRs.
The shortest interrupt latency is 3.25 instruction cycles, 800 ns
with a clock of 4.096 MHz. The longest interrupt latency for
a high priority interrupt results when a pending interrupt is
Vector Address
0x0003
0x000B
0x0013
0x001B
0x0023
0x002B
0x0033
0x003B
0x0043
0x0053
0x0063
0x004B
0x005B
Rev. 0 | Page 89 of 148
generated during a low priority interrupt RETI, followed by
a multiply instruction. This results in a maximum interrupt
latency of 16.25 instruction cycles, 4 μs with a clock of 4.096 MHz.
CONTEXT SAVING
When the 8052 vectors to an interrupt, only the program counter
is saved on the stack. Therefore, the interrupt service routine must
be written to ensure that registers used in the main program are
restored to their pre-interrupt state. Common SFRs that can be
modified in the ISR are the accumulator register and the PSW
register. Any general-purpose registers that are used as scratch
pads in the ISR should also be restored before exiting the
interrupt. The following example 8052 code shows how to
restore some commonly used registers:
GeneralISR:
; save the current Accumulator value
; save the current status and register bank
selection
; service interrupt
…
; restore the status and register bank
selection
; restore the accumulator
PUSH
PUSH
POP
POP
RETI
ACC
PSW
PSW
ACC
ADE5166/ADE5169