mitsubishi - Al Kossow's Bitsavers

~MITSUBISHI MICROCOMPUTERSMS0760·XXXP IMS0761.XXXPSINGLE-CHIP 4-BIT CMOS MICROCOMPUTERBASIC FUNCTION BLOCKSProgram Memory (ROM)This 1024-word X 8-bit mark programmable ROM can beprogrammed with machine instruction codes in accordancewith the customer's specifications.o address(OO) 16Reset startData Memory (RAM)This 48-word X 4-bit (192-bit) RAM is used to store bothprocessing and control data. One RAM word consists of 4bits with bit manipulation possible over the entire storagearea.~01a 1 2 33 2 1 0 3 2 1 a 3 2 1 a 3 2 1 0IIr--I"""1011Fig.3 RAM address mapNote: Y = 0-7 for the M50761-XXXP.1023 address( 3FF) 16Flg.1 ROM address mapProgram Counter (PC)This counter is to specify ROM addresses and the sequenceof read-out of instructions stored in the ROM. It is a10-bit polynomial counter.Fig.2 Program counter configurationNote: 1 a-bit configuration is also featured for the program counter in theM50761-XXXP.Stack Register (SK)This is used to temporarily store the contents of the PCwhile executing subroutines until the program returns to itsmain routine.Data Pointer (DP)These registers are used to designate RAM addresses andbit positions for output port D. Register X (the 2 most significantbits of the DP) designates the RAM file: register Y(the 4 least significant bits) designates the digit position ofthe RAM file.4-Bit' Arithmetic Logic UnitThis unit executes 4-bit arithmetic and logic operations. Itperforms subtraction, addition and logical comparisons.Register A and Carry Flag CYRegister A is a 4-bit accumulator that constitutes the basisfor arithmetic operations. The carry flag CY is used to storecarry or overflow after execution of arithmetic and logicaloperations by the arithmetic unit. It may also be used as a1-bit flag.Register BRegister B is composed of 4 bits and can be used as a 4-bit temporary storage register.TimerThe timer is implemented using a 7-bit counter which, afterrelease of reset, starts counting and divides the machinecycle by 100. It also sets the flag. Counting starts again afterthe flag has been set.The skip instruction (SNZT) can be used to test the flag.Both the timer and the flag can be reset using the systemreset and reset instruction (RSTM).• MITSUBISHI"ELECTRIC2-5