PIC16F54-I/P Microchip Technology Inc., PIC16F54-I/P Datasheet - Page 29

• Manufacturer Part Number: PIC16F54-I/P
• Description: 18 PIN, 768 B FLASH, 25 RAM, 12 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F54-I/P

• Cpu Speed: 5 MIPS
• Eeprom Memory: 0 Bytes
• Frequency: 20 MHz
• Input Output: 12
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 18-pin PDIP
• Programmable Memory: 750 Bytes
• Ram Size: 25 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

5.2
The Device Reset Timer (DRT) provides an 18 ms
nominal time-out on Reset regardless of the oscillator
mode used. The DRT operates on an internal RC
oscillator. The processor is kept in Reset as long as the
DRT is active. The DRT delay allows V
V
Oscillator circuits, based on crystals or ceramic resona-
tors, require a certain time after power-up to establish
a stable oscillation. The on-chip DRT keeps the device
in a Reset condition for approximately 18 ms after the
voltage on the MCLR/V
(V
the MCLR input are not required in most cases,
allowing for savings in cost-sensitive and/or space
restricted applications.
The device Reset time delay will vary from chip-to-chip
due to V
AC parameters for details.
The DRT will also be triggered upon a Watchdog Timer
time-out. This is particularly important for applications
using the WDT to wake the PIC16F5X from Sleep
mode automatically.
5.3
A Brown-out is a condition where device power (V
dips below its minimum value, but not to zero, and then
recovers. The device should be reset in the event of a
Brown-out.
To reset PIC16F5X devices when a Brown-out occurs,
external Brown-out protection circuits may be built, as
shown in Figure 5-6, Figure 5-7 and Figure 5-8.
FIGURE 5-6:
 2004 Microchip Technology Inc.
This circuit will activate Reset when V
Vz + 0.7V (where Vz = Zener voltage).
DD
IH
) level. Thus, external RC networks connected to
min. and for the chosen oscillator to stabilize.
33k
V
Device Reset Timer (DRT)
DD
Reset on Brown-Out
DD
, temperature and process variation. See
10k
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
PP
Q1
40k
pin has reached a logic high
MCLR
PIC16F5X
V
DD
DD
DD
goes below
to rise above
DD
)
FIGURE 5-7:
FIGURE 5-8:
V
This brown-out circuit is less expensive, although
less accurate. Transistor Q1 turns off when V
below a certain level such that:
This
Microchip Technology’s MCP809 microcontroller
supervisor. The MCP8XX and MCP1XX families
of supervisors provide push-pull and open collec-
tor outputs with both “active-high and active-low”
Reset pins. There are 7 different trip point
selections to accommodate 5V and 3V systems.
SS
MCP809
V
DD
brown-out
V
R1
R2
DD
RST
V
DD
V
DD
Capacitor
•
Bypass
protection
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 2
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 3
R1 + R2
R1
Q1
PIC16F5X
40k
= 0.7V
circuit
MCLR
PIC16F5X
V
DS41213C-page 27
DD
MCLR
V
PIC16F5X
DD
employs
DD
is