mitsubishi - Al Kossow's Bitsavers

MITSUBISHI MICROCOMPUTERSMSM80C49-XXXP/MSM80C39P-6SINGLE-CHIP a-BIT CMOS MICROCOMPUTERLow power dissipation mode(1 ) HALT modeIt will b.e. in HALT mode when HALT instruction is executedand program -execution is stopped. In HALTlmode, only the basic clock operates and the others areall in the halt state. MCU keeps the contents of the registersin the state before the execution of HALT instrucitons.The pin conditions are shown below.Table 1PinData busPorts1,2ALEPSEN.RDWR. PROGT¢lT1(counter input)(Timer)ConditionsOutput mode : Data outputInput mode: High inpedence(Input mode for M5M80C39P-6)Port data outputLHProvided clock is continuedThe first pulse input is effective.After the reset of Halt mode. the count continues.Halt(2) Standby modeIt will be in Stnadby mode when STBY input goes "L"after setting RESET ipput to "~". In standby mode, alloperations including clock stop, and only the contentsof the buit-in RAM are maintained. For the standbymode reset, let STBY pin "H", Keeping RESET inputlow, and then let RESET input input "H". After that theinternal state is inilialized and program excuition startsfrom address O.Control method of standby mode (Example)Place the capacitor to RESET pin, as shown in Fig 2, inorder to make th standby mode control easier, so thatthe standby mode can be controlled by only contollingSTBY pin.M5M80C49-XXXp·M5M80C39P-6HALT stateL-+------------------------~LL'------------1- 1 count up-----+- 1 count upL-+ ____ ..H-+-----------------------+_H-+----..H-+------........--------""'1- 1 count upFig. 2Control circuit example for standby modeFig. 1Counter operation in the HALT modeThe HALT mode can be cleared by the following 2methods(i) By RESET inputWhen RESET input goes "L", an internal state is initializedas same as the normal reset operation, andthe program starts from address O.(II) BylNT inputWhen INT input gose "L",and if it is in the interuptenable state, the interrupt sequence will start afterexecuting the 2en instruction following HALT instructions.If is the interrupt disable state, the program exeutionstarts from the next address to HALT instructions.4-48 • MITSUBISH. I"'ELECTRIC