Preliminary W742E81A/W742C81A
Bit 3, Bit 2, Bit 1, Bit 0 Data memory bank preselect bits:
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 W742E81A/W742C81A 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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Publication Release Date: April 2000
Revision A1