Release Of Halt Mode By A Maskable Interrupt Request - NEC PD78212 User Manual

(2) Release by a maskable interrupt request
Only maskable interrupts with 0 in the interrupt mask flag can be used to release HALT mode. If the interrupt
priority status flag (ISP) is set to 0 (only high-priority interrupts are enabled), only interrupts with 0 in the
priority designation flag (high priority) can release HALT mode. Macro services are, however, executed
regardless of their priorities (an interrupt to be generated at the end of each macro service is subject to priority
control).
Once HALT mode has been released, processing branches to the interrupt handling program if the interrupt
request enable flag (IE) is set to 1. If the IE flag is set to 0, processing is resumed from the instruction
subsequent to that which specified HALT mode.
When a macro service is requested, HALT mode is temporarily released to execute the macro service. After
the macro service is executed, HALT mode is resumed. Once the macro service has been executed the
specified number of times, subsequent operations depend on the IE flag, ISP flag, and priority designation
flag.
Table 14-3 Release of HALT Mode by a Maskable Interrupt Request
Releasing source
Maskable
vectored interrupt
request
Macro service
request
Remark MK×× : Interrupt mask flag
PR×× : Priority designation flag
IE : Interrupt request enable flag
ISP : Interrupt priority status flag
(3) Release by RESET input
The program is resumed from the reset vector address in the same way as for an ordinary reset operation,
except that the contents of internal RAM are the same as those existing immediately before entering HALT
mode.
MK×× PR×× IE ISP
×
0 0 1
×
0 1 1
×
0 0 0
×
0 0 1
×
0 1 0
× × ×
1
×
0 0 1
×
0 1 1
×
0 0 0
×
0 0 1
×
0 1 0
× × ×
1
Chapter 14 Standby Function
Operation
Handling a vectored interrupt
Executing the instruction at the next address (holding the
interrupt request)
Continuing HALT mode
Executing the macro service
When the end conditions are satisfied, a vectored interrupt
is handled.
When the end conditions are not satisfied, HALT mode is
resumed.
Executing the macro service
When the end conditions are satisfied, the instruction at the
next address is executed.
When the end conditions are not satisfied, HALT mode is
resumed.
Executing the macro service then resuming HALT mode
Continuing HALT mode
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