uPD789074 Subseries 8-Bit Single-Chip Microcontrollers UD - Home

CHAPTER 10 INTERRUPT FUNCTIONS(1) Interrupt request flag registers 0 and 1 (IF0 and IF1)An interrupt request flag is set to 1 when the corresponding interrupt request is issued, or when the relatedinstruction is executed. It is cleared to 0 when the interrupt request is acknowledged, when a RESET signalis input, or when a related instruction is executed.IF0 and IF1 are set with a 1-bit or 8-bit memory manipulation instruction.RESET input clears IF0 and IF1 to 00H.Figure 10-2. Format of Interrupt Request Flag RegisterSymbol 7 6 Address After reset R/WIF00 0 STIF20 SRIF20 PIF2 PIF1 PIF0 WDTIF7 6 5 4 3 2 FFE0H 00H R/WIF1 0 0 0 0 0 0 TMIF90 TMIF80 FFE1H 00H R/W××IF×01No interrupt request signal has been issued.Interrupt request flagAn interrupt request signal has been issued; an interrupt request has been made.Cautions 1. Bits 6 and 7 of IF0 and bits 2 to 7 of IF1 must all be set to 0.2. The WDTIF flag can be read- and write-accessed only when the watchdog timer isbeing used as an interval timer. It must be cleared to 0 if the watchdog timer is used inwatchdog timer mode 1 or 2.3. When port 2 is being used as an output port, and its output level is changed, an interruptrequest flag is set, because this port is also used as an external interrupt input. To useport 2 in output mode, therefore, the interrupt mask flag must be preset to 1.154User’s Manual U14801EJ3V1UD