W742S81A Datasheet, PDF (10/47 Pages) Winbond – 4 BIT MICROCONTROLLER

W742S81A
0000 = Data bank 0 (000H - 07FH)
0001 = Data bank 1 (080H - 0FFH)
0010 = Data bank 2 (100H - 17FH)
0011 = Data bank 3 (180H - 1FFH)
0100 = Data bank 4 (200H - 27FH)
0101 = Data bank 5 (280H - 2FFH)
0110 = Data bank 6 (300H - 37FH)
0111 = Data bank 7 (380H - 3FFH)
1000 = Data bank 8 (400H - 47FH)
1001 = Data bank 9 (480H - 4FFH)
1010 = Data bank A (500H - 57FH)
1011 = Data bank B (580H - 5FFH)
1100 = Data bank C (600H - 67FH)
1101 = Data bank D (680H - 6FFH)
1110 = Data bank E (700H - 77FH)
1111 = Data bank F (780H - 7FFH)
6.5 Accumulator (ACC)
The accumulator (ACC) is a 4-bit register used to hold results from the ALU and transfer data between the
memory, I/O ports, and registers.
6.6 Arithmetic and Logic Unit (ALU)
This is a circuit which performs arithmetic and logic operations. The ALU provides the following
functions:
•Logic operations: ANL, XRL, ORL
•Branch decisions: JB0, JB1, JB2, JB3, JNZ, JZ, JC, JNC, DSKZ, DSKNZ, SKB0, SKB1, SKB2, SKB3
•Shift operations: SHRC, RRC, SHLC, RLC
•Binary additions/subtractions: ADC, SBC, ADD, SUB, ADU, DEC, INC
After any of the above instructions are executed, the status of the carry flag (CF) and zero flag (ZF) is
stored in the internal registers. CF can be read out by executing MOV R, CF.
6.7 Main-Oscillator
The W742S81A provides a crystal or RC oscillation circuit to generate the system clock through external
connections. If a crystal oscillator is used, The 3.58 MHz or 400KHz crystal must be connected to XIN1
and XOUT1, and a capacitor must be connected to XIN1 and VSS if an accurate frequency is needed.
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