W741C260 Datasheet, PDF (8/92 Pages) Winbond – 4-BIT MICROCONTROLLER

W741C260
2. Page Register (PAGE)
The page register is organized as a 4-bit binary register. The bit descriptions are as follows:
3
2
1
0
PAGE R/W R/W R/W R/W
Note: R/W means read/write available.
Bit 3 is reserved.
Bit 2, Bit 1, Bit 0 Indirect addressing mode preselect bits:
000 = Page 0 (00H−0FH)
010 = Page 2 (20H−2FH)
100 = Page 4 (40H−4FH)
110 = Page 6 (60H−6FH)
001 = Page 1 (10H−1FH)
011 = Page 3 (30H−3FH)
101 = Page 5 (50H−5FH)
111 = Page 7 (70H−7FH)
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.
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. Otherwise CF can be stored or be read out by executing MOVA R, CF
or MOV CF, R.
Clock Generator
The W741C260 provides two oscillation circuits, main-oscillator and sub-oscillator. The main-
oscillator can select the crystal or RC oscillation circuit by option codes to generate the system clock
through external connections. If a crystal oscillator is used, a crystal or a ceramic resonator must be
connected to XIN1 and XOUT1, and a capacitor must be connected if an accurate frequency is
needed. When the oscillator is used, a high-frequency clock (400 KHz to 4 MHz) or low-frequency
clock (32 KHz) can be selected for the system clock by means of option codes. If the RC oscillator is
used, a resistor must be connected to XIN1 and XOUT1, and the high/low frequency clock option
must be selected to suit the operation frequency. The sub-oscillator must be connected to a 32.768
KHz crystal through XIN2 and XOUT2 external pins when the dual-clock operation mode is selected
by option code. The connection is shown in Figure 3. One machine cycle consists of a four-state
system clock sequence and can run up to 1 µS with a 4 MHz system clock.
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