Z86318 Datasheet, PDF (21/26 Pages) Zilog, Inc. – Z8 MCU 8-BIT MICROCONTROLLER

Z86318
Z8^® MCU 8-Bit Microcontroller
Watch-Dog Timer (WDT). The WDT is initially enabled by Low-Voltage Protection (V_LV). The device will function
executing the WDT instruction and it is refreshed by sub- normally between 6.0V and 4.0V under all specified condi-
sequent WDT instruction executions. Note: Once the WDT
has been enabled, it cannot be disabled. The time-out pe-
tions. Below 4.0V, the device is still internally functional un-
til the Low Voltage trip point (V_LV) is reached; however, it
1
riod of the WDT is 24 ms. The WDT instruction affects the is not guaranteed to meet all AC and DC Characteristics.
Zero (Z), Sign (S), and Overflow (V) flags. The WDT can When the supply voltage drops below V_LV, an automatic
be permanently enabled (ROM mask option) upon MCU hardware reset occurs, re-initializing the Z86318. The
power-up.
Low-Voltage Protection feature may be selected as a
ROM mask option.
Opcode WDT (5FH). Execution of WDT clears the WDT
counter. This must be done at least every 24 ms, other- The actual V_LV is a function of temperature, operating fre-
wise, the WDT times out and generates a reset. This gen- quency and process parameters. A typical example of the
erated reset is the same as a power-on reset of 6.0 ms, V_LV trip-point function at ambient temperature for a fre-
plus 18 clock cycles.
quency of 4 MHz is illustrated in Figure 18.
Vcc
(Volts)
2.80
2.75
2.70
2.65
2.60
2.55
L_LV (Typical)
2.50
–5 0
5 10 15 20 25 30 35 40 45
Temperature (°C)
Figure 18. Typical Z86318 V_LV Versus Temperature
PRELIMINARY
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