P8XCL580HFT View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'P8XCL580HFT' PDF : 80 Pages View PDF
Philips Semiconductors
Low voltage 8-bit microcontrollers with
UART, I2C-bus and ADC
Product specification
P80CL580; P83CL580
17 INTERRUPT SYSTEM
External events and the real-time-driven on-chip
peripherals require service by the CPU at unpredictable
times. To tie the asynchronous activities of these functions
to normal program execution a multiple-source,
two-priority-level, nested interrupt system is provided.
The system is shown in Fig.27. The P8xCL580
acknowledges interrupt requests from fifteen sources as
follows:
• INT0 to INT8
• Timer 0, Timer 1 and Timer 2
• I2C-bus serial I/O
• UART
• ADC.
Each interrupt vectors to a separate location in Program
Memory for its service routine. Each source can be
individually enabled or disabled by corresponding bits in
the Interrupt Enable Registers (IEN0 and IEN1).
The priority level is selected via the Interrupt Priority
Registers (IP0 and IP1). All enabled sources can be
globally disabled or enabled. Figure 27 shows the interrupt
system.
17.1 External interrupts INT2 to INT8
Port 1 lines serve an alternative purpose as seven
additional interrupts INT2 to INT8. When enabled, each of
these lines may wake-up the device from the Power-down
mode. Using the Interrupt Polarity Register (IX1), each pin
may be initialized to be either active HIGH or active LOW.
IRQ1 is the Interrupt Request Flag Register. If the interrupt
is enabled, each flag will be set on an interrupt request but
must be cleared by software, i.e. via the interrupt software
or when the interrupt is disabled.
Port 1 interrupts are level sensitive. A Port 1 interrupt will
be recognized when a level (HIGH or LOW depending on
the Interrupt Polarity Register) on P1.n is held active for at
least one machine cycle. The interrupt request is not
serviced until the next machine cycle. Figure 28 shows the
external interrupt system.
17.2 Interrupt priority
Each interrupt source can be set to either a high priority or
to a low priority. If a low priority interrupt is received
simultaneously with a high priority interrupt, the high
priority interrupt will be dealt with first.
If interrupts of the same priority are requested
simultaneously, the processor will branch to the interrupt
polled first, according to the sequence shown in Table 34
and in Fig.27. The ‘vector address’ is the ROM location
where the appropriate interrupt service routine starts.
Table 34 Interrupt vector polling sequence
SYMBOL
X0 (first)
S1
X5
T0
T2
X6
X1
X2
X7
T1
X3
X8
SO
X4
ADC (last)
VECTOR
ADDRESS (HEX)
SOURCE
0003
002B
External 0
I2C port
0053
External 5
000B
Timer 0
0033
Timer 2
005B
External 6
0013
External 1
003B
External 2
0063
External 7
001B
Timer 1
0043
External 3
006B
External 8
0023
UART
004B
External 4
0073
ADC
A low priority interrupt routine can only be interrupted by a
high priority interrupt. A high priority interrupt routine
cannot be interrupted.
1997 Mar 14
45
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