MITSUBISHI MICROCOMPUTERS
M37207MF-XXXSP/FP, M37207M8-XXXSP
M37207EFSP/FP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
and ON-SCREEN DISPLAY CONTROLLER
17
INTERRUPTS
Interrupts can be caused by 15 different sources consisting of 3 ex-
ternal, 10 internal, 1 software, and reset. Interrupts are vectored in-
terrupts with priorities as shown in Table 1. Reset is also included in
the table because its operation is similar to an interrupt.
When an interrupt is accepted,
(1) The contents of the program counter and processor status
register are automatically stored into the stack.
(2) The interrupt disable flag I is set to “1” and the corresponding
interrupt request bit is set to “0.”
(3) The jump destination address stored in the vector address enters
the program counter.
Other interrupts are disabled when the interrupt disable flag is set to
“1.”
All interrupts except the BRK instruction interrupt have an interrupt
request bit and an interrupt enable bit. The interrupt request bits are
in interrupt request registers 1 and 2 and the interrupt enable bits are
in interrupt control registers 1 and 2. Figures 10 to 13 show the inter-
rupt-related registers.
Interrupts other than the BRK instruction interrupt and reset are ac-
cepted when the interrupt enable bit is “1,” interrupt request bit is “1,”
and the interrupt disable flag is “0.” The interrupt request bit can be
set to “0” by a program, but not set to “1.” The interrupt enable bit can
be set to “0” and “1” by a program.
Reset is treated as a non-maskable interrupt with the highest priority.
Figure 9 shows interrupt control.
Interrupt Causes
(1) VSYNC and CRT interrupts
The VSYNC interrupt is an interrupt request synchronized with
the vertical sync signal.
The CRT interrupt occurs after character block display to the CRT
is completed.
(2) INT1, INT2 interrupts
With an external interrupt input, the system detects that the level
of a pin changes from “L” to “H” or from “H” to “L,” and generates
an interrupt request. The input active edge can be selected by
bits 3 and 4 of the interrupt interval determination control register
(address 00D816) : when this bit is “0,” a change from “L” to “H” is
detected; when it is “1,” a change from “H” to “L” is detected.
Note that all bits are cleared to “0” at reset.
(3) Timer 1, 2, 3 and 4 interrupts
An interrupt is generated by an overflow of timer 1, 2, 3 or 4.
(4) Serial I/O interrupt
This is an interrupt request from the clock synchronous serial
I/O function.
Priority
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Vector Addresses
FFFF16, FFFE16
FFFD16, FFFC16
FFFB16, FFFA16
FFF916, FFF816
FFF716, FFF616
FFF516, FFF416
FFF316, FFF216
FFF116, FFF016
FFEF16, FFEE16
FFED16, FFEC16
FFEB16, FFEA16
FFE716, FFE616
FFE316, FFE216
FFDF16, FFDE16
Interrupt Source
Reset
CRT interrupt
INT1 interrupt
INT2 interrupt
Timer 4 interrupt
f(XIN)/4096 interrupt
VSYNC interrupt
Timer 3 interrupt
Timer 2 interrupt
Timer 1 interrupt
Serial I/O interrupt
Multi-master I
2
C-BUS interface interrupt
Timer 5 · 6 interrupt
BRK instruction interrupt
Remarks
Non-maskable
Active edge selectable
Active edge selectable
Active edge selectable
Source switch by software (See note)
Non-maskable (software interrupt)
Table 1. Interrupt Vector Addresses and Priority
Note : Switching a source during a program causes an unnecessary interrupt. Therefore, set a source at initializing of program.
