Z8F640x/Z8F480x/Z8F320x/Z8F240x/Z8F160x
Z8 Encore!
®
28
threshold voltage, V
VBO
) and forces the device into the Reset state. While the supply volt-
age remains below the Power-On Reset voltage threshold (V
POR
), the VBO block holds
the Z8F640x family device in the Reset state.
After the supply voltage again exceeds the Power-On Reset voltage threshold, the
Z8F640x family device progresses through a full System Reset sequence, as described in
the Power-On Reset section. Following Power-On Reset, the
POR
status bit in the Watch-
Dog Timer Control (WDTCTL) register is set to 1. Figure 63 illustrates Voltage Brown-
Out operation. Refer to the
Electrical Characteristics
chapter for the VBO and POR
threshold voltages (V
VBO
and V
POR
).
Stop mode disables the Voltage Brown-Out detector.
VCC = 3.3V
V
POR
V
VBO
Program
Execution
Voltage
Brownout
Program
Execution
VCC = 3.3V
WDT Clock
Crystal Oscillator
XOUT
Internal RESET
signal
POR
counter delay
XTAL
counter delay
Figure 63. Voltage Brown-Out Reset Operation (not to scale)
Watch-Dog Timer Reset
If the device is in normal or Halt mode, the Watch-Dog Timer can initiate a System Reset
at time-out if the
WDT_RES
Option Bit is set to 1. This is the default (unprogrammed) set-
ting of the
WDT_RES
Option Bit. The
WDT
status bit in the WDT Control register is set to
signify that the reset was initiated by the Watch-Dog Timer.
PS017610-0404
Reset and Stop Mode Recovery
ZILOG [ ZILOG, INC. ]
