NEC UPD789026 Series, User Manual

Page: 154 / 213

CHAPTER 10 INTERRUPT FUNCTIONS
User's Manual U11919EJ3V0UM00
154
(2) Interrupt mask flag registers (MK0 and MK1)
The interrupt mask flag is used to enable/disable the corresponding maskable interrupt servicing.
MK0 and MK1 are set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets MK0 and MK1 to FFH.
Figure 10-3. Interrupt Mask Flag Register Format
0
1
1 TMMK00 STMK00 SRMK00 PMK2 PMK1 PMK0 TMMK4 MK0
R/W
FFE4H FFH R/W
Symbol
Address After Reset
Interrupt Servicing Control
Interrupt servicing enabled
Interrupt servicing disabled
××
MK
×
<6> <5> <4> <3> <2> <1> 7 <0>
TMMK20 1 1 1 1 1 1 KRMK00 MK1 FFE5H FFH R/W
6 5 4 3 2 1 <7> <0>
Cautions 1. Be sure to set bit 7 of MK0 and bits 1 to 6 of MK1 to 1.
2. IF the TMMK4 flag is read when a watchdog timer is used in watchdog timer mode 1 or
2, its value becomes undefined.
3. Because port 3 has an alternate function as the external interrupt input, when the
output level is changed by specifying the output mode of the port function, an
interrupt request flag is set. Therefore, 1 should be set in the interrupt mask flag
before using the output mode.
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