SM39R16A3 Datasheet, PDF (50/87 Pages) SyncMOS Technologies,Inc – 16KB on-chip program memory

10. Interrupt
SM39R16A3
8-Bit Micro-controller
with 16KB ISP Flash
& 512B RAM embedded
The SM39R16A3 provides 14 interrupt sources with four priority levels. Each source has its own request flag(s) located
in a special function register. Each interrupt requested by the corresponding flag could individually be enabled or
disabled by the enable bits in SFR’s IEN0, IEN1, and IEN2.
When the interrupt occurs, the engine will vector to the predetermined address as shown in Table 10-1. 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 an RETI is performed, the processor will return to the instruction that would have
been next when 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, and then
samples are polled by hardware. If the sample indicates a pending interrupt when the interrupt is enabled, then
interrupt request flag is set. On the next instruction cycle the interrupt will be acknowledged by hardware forcing an
LCALL to appropriate vector address.
Interrupt response will require a varying amount of time depending on the state of microcontroller when the interrupt
occurs. If microcontroller 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 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 for perform the
LCALL.
Table 10-1: Interrupt vectors
Interrupt Request Flags
Interrupt Vector
Address
1 _{IE0 – External interrupt 0}
0003h
2 _{TF0 – Timer 0 interrupt}
000Bh
3 _{IE1 – External interrupt 1}
0013h
4 _{TF1 – Timer 1 interrupt}
001Bh
5 _{RI/TI – Serial channel interrupt}
0023h
6 _{TF2/EXF2 – Timer 2 interrupt}
002Bh
7 _{PWMIF – PWM interrupt}
0043h
8 _{SPIIF – SPI interrupt}
004Bh
9 _{ADCIF – A/D converter interrupt}
0053h
10 KBIIF – keyboard Interface interrupt
005Bh
11 LVIIF – Low Voltage Interrupt
0063h
12 IICIF – IIC interrupt
006Bh
13 _{WDTIF – Watchdog interrupt}
008Bh
14 Comparator interrupt
0093h
Interrupt Number
*(use Keil C Tool)
0
1
2
3
4
5
8
9
10
11
12
13
17
18
* See Keil C about C51 User’s Guide about Interrupt Function description
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M065
Ver F SM39R16A3 06/30/2015
- 50 -