EZ80F91MCU ZILOG [Zilog, Inc.], EZ80F91MCU Datasheet - Page 71

• Manufacturer Part Number: EZ80F91MCU
• Description: eZ80Acclaim-TM Flash Microcontrollers
• Manufacturer: ZILOG [Zilog, Inc.]

Figure 3. Power-On Reset Operation
PS019209-0504
Internal RESET
System Clock
V
CC
Power-On Reset
Voltage Brown-Out Reset
= 0.0V
Signal
V
V
POR
VBO
A Power-On Reset (POR) occurs each time the supply voltage to the part rises
from below the voltage brown-out threshold (V
threshold (V
tinuous RESET signal to the Reset controller until the supply voltage (V
exceeds the POR voltage threshold. After V
log delay element briefly maintains the RESET signal to the Reset controller. After
this analog delay element times out, the Reset controller holds the eZ80F91 in
RESET until the RESET mode timer expires. POR operation is illustrated in
Figure 3. The signals in Figure 3 are not drawn to scale, but are for illustration pur-
poses only.
If, after program execution begins, the supply voltage (V
age brown-out threshold (V
circuitry detects the low supply voltage and initiates a RESET via the Reset con-
troller. The eZ80F91 remains in RESET until the supply voltage again returns
above the POR voltage threshold (V
internal RESET signal. The VBO circuitry rejects very short negative brown-out
pulses to prevent spurious RESET events.
Oscillator
POR
Startup
). The internal bandgap-referenced voltage detector sends a con-
T
ANA
P R E L I M I N A R Y
VBO
), the eZ80F91 device resets. The VBO protection
RESET mode timer delay
POR
) and the Reset controller releases the
CC
VBO
rises above V
) to above the POR voltage
CC
Product Specification
) drops below the volt-
POR
Program Execution
, an on-chip ana-
eZ80F91 MCU
V
CC
CC
)
= 3.3V
Reset
52