W741C260 Datasheet, PDF (10/92 Pages) Winbond – 4-BIT MICROCONTROLLER

W741C260
Mask Option (High/Low Freq.)
HOLD
SCR.0
XIN1
XOUT1
Fm
Main Oscillator
Fs
Fosc
System Clock
Generator
T1
T2
T3
SCR.1
T4
enable/disable
Divider 0
XIN2
XOUT2
Sub-oscillator
Mask Option
(Single/Dual Clock) _{enable/disable}
Fosc/32
Fosc
Mask Option (High/Low Freq.)
LCD Frequency
Selector
FLCD
Mask Option (Single/Dual Clock)
Divider 1
INT4
HCF.4
SCR.3 (14/13 bit)
Figure 4. The Dual Clock Operation Mode Control Diagram
Divider
Each divider is organized as a 14-bit binary up-counter designed to generate periodic interrupts.
When the main oscillator starts action, the divider0 is incremented by each clock (FOSC). When an
overflow occurs, the divider0 event flag is set to 1 (EVF.0 = 1). The interrupt is executed if the
divider0 interrupt enable flag has been set (IEF.0 = 1), and the hold state is terminated if the hold
release enable flag has been set (HEF.0 = 1). The last 4-stage of the divider0 can be reset by
executing a CLR DIVR0 instruction. If the main oscillator is connected to the 32768 Hz crystal, the
EVF.0 will be set to 1 periodically at each 500 mS interval.
If the sub-oscillator is enabled, the divider1 is incremented by each clock (Fs). When an overflow
occurs, the divider1 event flag is set to 1 (EVF.4 = 1). The interrupt is executed if the divider1
interrupt enable flag has been set (IEF.4 = 1), and the hold state is terminated if the hold release
enable flag has been set (HEF.4 = 1). There are two time periods (250 mS & 500 mS) that can be
selected by setting the SCR.3 bit. When SCR.3 = 0 (default), the 500 mS period time is selected;
when SCR.3 = 1, the 250 mS period time is selected.
Watchdog Timer (WDT)
The watchdog timer (WDT) is organized as a 4-bit up counter and is designed to protect the program
from unknown errors. The WDT is enabled when the corresponding option code bit of the WDT is set
to 1. If the WDT overflows, the chip will be reset. At initial reset, the input clock of the WDT is
FOSC/1024. The input clock of the WDT can be switched to FOSC/16384 (or FOSC/1024) by executing
the SET PMF, #08H (or CLR PMF, #08H) instruction. The contents of the WDT can be reset by the
instruction CLR WDT. In normal operation, the application program must reset WDT before it
overflows. A WDT overflow indicates that the operation is not under control and the chip will be reset.
The WDT minimun overflow period is 468.75 mS when the system clock (FOSC) is 32 KHz and WDT
clock input is FOSC/1024. When the corresponding option code bit of the WDT is set to 0, and the
WDT function is disabled. The organization of the Divider0 and watchdog timer is shown in Figure 4.
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