Mitsubishi DS5000TK Interrupt Priorities, Interrupt Priority Control Bits ±3 Bit Description

USER'S GUIDE

INTERRUPT PRIORITIES

The Secure Microcontroller provides a three priority interrupt scheme. Multiple priority levels allow higher priority sources to interrupt lower priority ISRs. The Power±fail Warning Interrupt automatically has the highest priority if enabled. The remaining interrupts can be programmed by the user to either high or low priority. The priority scheme woks as follows. The ISR for a low priority source can be interrupted by a high priority source. A low priority ISR can not be interrupted by another low priory source. Neither can a high priority ISR be interrupted by a another high priority source. The PFW source will interrupt any ISR if activated.

In the case of simultaneous interrupt requests, the mi- crocontroller has a natural scheme to arbitrate. First, if high and low priority interrupt requests are received simultaneously, then the high priority source will be serviced. If two or more requests from equal priority sources are received, the following natural priority scheme will be used to arbitrate.

Each interrupt priority is determined by an individual bit as shown below. Setting the appropriate bit to a logic 1 will cause that interrupt to be high priority.

PRIORITY	FLAG	INTERRUPT SOURCE
1	PFW	Power±fail Warning
2	IE0	External Interrupt 0
3	TF0	Timer 0 Interrupt
4	IE1	External Interrupt 1
5	TF1	Timer 1 Interrupt
6	RI+TI	Serial I/O Interrupt

INTERRUPT PRIORITY CONTROL BITS Figure 11±3

Bit Description:

All bits are read/write at any time and are cleared to 0 following any hardware reset.

IP.4:	PS
ªSerial Port Priorityº:	Programs Serial Port interrupts for high priority when set to 1. Low priority is
	selected when cleared to 0.
IP.3:	PT1
ªTimer 1 Priorityº:	Programs Timer 1 interrupt for high priority when set to 1. Low priority is se-
	lected when cleared to 0.
IP.2:	PX1
ªExt. Int. 1 Priorityº:	Programs External Interrupt 1 for high priority when set to 1. Low priority is
	selected when cleared to 0.
IP.1:	PT0
ªTimer 0 Priorityº:	Program Timer 0 interrupt for high priority when set to 1. Low priority is se-
	lected when cleared to 0.
IP.0:	PX0
ªExt. Int. 0 Priorityº:	Programs External Interrupt 0 for high priority when set to 1. Low priority is
	selected when cleared to 0.
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