NEC PD75402A Manuale Utente
128
CHAPTER 6. INTERRUPT FUNCTIONS
6.2
INTERRUPT SOURCE TYPES AND VECTOR TABLE
The
µ
PD75402A’s interrupt source types and interrupt vector table are shown in Table 6-1 and Fig. 6-2.
Table 6-1 Interrupt Request Source Types
Vectored Interrupt Request Signal
(Vector Table Address)
Interrupt Request
Generation Source
Interrupt
Priority
*
1
Internal/
External
1
2
3
Internal
External
Internal
External
INTBT
(Basic time interval signal from basic interval timer)
INT0 (INT0 pin input specified edge detection)
INTCSI (Serial data transfer termination signal)
INT2
*
2 (INT2 pin input rising edge detection)
VRQ1(0002H)
VRQ2(0004H)
VRQ3(0008H)
Testable input signal (sets) IRQ2 flag)
*
1. The interrupt priority is the order of precedence when multiple interrupt requests occur simultaneously.
2. A test source. This is affected by an interrupt enable flag in the same way as an interrupt source, but no
vectored interrupt is generated.
Fig. 6-2 Interrupt Vector Table
★
0 0 0 8 H
0
0
0
0
0
INTCSI start address (high-order 3 bits)
INTCSI start address (low-order 8 bits)
0 0 0 2 H
0
0
0
0
0
INTBT start address (high-order 3 bits)
INTBT start address (low-order 8 bits)
0 0 0 4 H
0
0
0
0
0
INT0 start address (high-order 3 bits)
INT0 start address (low-order 8 bits)
Address
The interrupt priority shown in the table shows the order in which interrupts are executed when multiple interrupt
requests are generated simultaneously or when multiple interrupt requests are pending.
The vector table contains the interrupt service routine start addresses. Vector table setting is performed by the
VENTn assembler pseudoinstruction.
Example
INTBT vector table setting.
VENT1
GOTOBT
↑
↑
Address 0002
Symbol indicating start address
vector table
of interrupt service routine
Note
The vector table address specified by VENTn (n = 1, 2 and 4) is address 2n.
Example
INTBT and INT0 vector table setting.
VENT1
GOTOBT
VENT2
GOTO0