Part Number: PIC18F252-I/SP

Manufacturer: Microchip Technology

Description: IC MCU 8BIT 32KB FLASH 28SPDIP

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Technical Specifications of PIC18F252-I/SP

Datasheet  PIC18F252-I/SP datasheet
Category Integrated Circuits (ICs)
Family Embedded – Microcontrollers
Manufacturer Microchip Technology
Series PIC? 18F
Packaging Tube
Part Status Not For New Designs
Core Processor PIC
Core Size 8-Bit
Speed 40MHz
Connectivity I2C, SPI, UART/USART
Peripherals Brown-out Detect/Reset, LVD, POR, PWM, WDT
Number of I/O 23
Program Memory Size 32KB (16K x 16)
Program Memory Type FLASH
EEPROM Size 256 x 8
RAM Size 1.5K x 8
Voltage – Supply (Vcc/Vdd) 4.2 V ~ 5.5 V
Data Converters A/D 5x10b
Oscillator Type External
Operating Temperature -40°C ~ 85°C (TA)
Package / Case 28-DIP (0.300″, 7.62mm)
Supplier Device Package 28-SPDIP

PIC18F252-I/SP Introduction

The PIC18F252-I/SP is a microcontroller device that provides an Oscillator Switching Feature, which allows low-frequency clock sources to be used as the system clock. This feature is made possible by the Timer1 oscillator, which, when connected to a low-frequency crystal, can enter a Low Power Execution mode. The device also has a SLEEP mode, which disables on-chip features that run during SLEEP to reduce power consumption. Power-up delays are managed by two timers, the Power-up Timer (PWRT) and the Oscillator Start-up Timer (OST). The PWRT provides a preset delay of 72 ms during power-up, while the OST provides a delay of 1024 oscillator cycles to stabilize the crystal resonator or oscillator. In the event of a power spike, the device’s Power-on Reset (POR) circuitry is activated, which requires external RC components to generate a POR delay. The device also has Brown-out Reset (BOR) circuitry that can reset the chip if VDD drops below a certain threshold.

Detailed Description

● Oscillator Switching Feature

The PIC18FXX2 devices provide a feature that lets you use a low-frequency clock source instead of the primary oscillator as the system clock. The Timer1 oscillator provides this backup function for PIC18FXX2 devices. After connecting a low-frequency crystal (32 kHz, for instance) to the Timer1 oscillator pins and turning on the Timer1 oscillator, the device can enter a Low Power Execution mode.

● Effects of SLEEP Mode on the On-Chip Oscillator

After receiving a SLEEP instruction, the device will wait until the beginning of the next instruction cycle before turning on the on-chip clocks and oscillator (Q1 state). The OSC1 and OSC2 signals will cease to oscillate once the oscillator is turned off. As SLEEP mode disables the transistor switching currents, it uses the least amount of power possible (only leakage currents). Turning on any on-chip features running during SLEEP will increase current consumption. If the user is in SLEEP mode, they can be roused by an external RESET, a Watchdog Timer Reset, or an interrupt.

● Power-up Delays

There is no need for external RESET circuitry thanks to using two timers to postpone power. Unless the device’s power supply and clock are stable, the device will remain in RESET, as shown by the delays. Refer to Section 3.0 for more details on RESET’s functionality. The Power-up Timer (PWRT) is the first timer, and it provides a preset delay of 72 ms (nominal) during power-up if desired (POR and BOR). Oscillator Start-up Timer (OST) is a second timer programmed to keep the chip in RESET until the crystal oscillator is steady.

The time-out sequence after a Power-on Reset differs depending on whether the PLL is activated (HS/PLL Oscillator mode). Here is the time-out procedure: After a predetermined amount of time has elapsed (a POR), the PWRT time-out is triggered. This triggers the Oscillator Start-up Timer (OST). Yet that’s still not enough time for the PLL to lock at those frequencies. To provide the PLL sufficient time to lock to the incoming clock frequency, a fixed 2 ms (nominal) time-out is provided by the PWRT timer.

● Power-On Reset (POR)

If a spike in VDD is observed, an on-chip Power-on Reset pulse will be generated. Connecting the MCLR pin to VDD (either directly or via a resistor) will activate the POR circuitry. To generate a Power-on Reset delay, external RC components are typically required. The rate of increase of VDD must not be less than that which is required (parameter D004). Figure 3-2 depicts a gradual increase in pressure. Device operating conditions (voltage, frequency, temperature, etc.) must be met to guarantee operation once normal operation has begun (i.e., once the RESET condition has been cleared). If they aren’t met, you have to keep the gadget in RESET mode until they are.

● Power-up Timer (PWRT)

The Power-up Timer only activates during the first POR power-on, which supplies a nominal time-out (parameter 33). An RC oscillator is used to power the Power-up Timer. If the PWRT remains on, the chip will remain in RESET mode. Due to the PWRT’s time lag, VDD can safely increase to safe levels. A configuration bit is provided to enable/disable the PWRT. Power-on delays will change from chip to chip based on VDD, temperature, and manufacturing process.

● Oscillator Start-up Timer (OST)

After the pre-delay for the PWRT has elapsed, a delay of 1024 oscillator cycles (from the OSC1 input) is provided by the Oscillator Start-up Timer (OST) (parameter 32). The crystal resonator or oscillator will have started and steadied at this point. Only on Power-on Reset or upon waking from SLEEP will the OST time-out be activated, which limits its use to the XT, LP, and HS modes.

● PLL Lock Time-out

When the PLL is active, the time-out sequence after a Power-on Reset is distinct from the sequences that occur in the other Oscillator modes. The Power-up Timer is employed to give a defined time-out to allow the PLL to synchronize with the main oscillator’s frequency. This component of the Power-up Timer is utilized to give a fixed time-out. This is accomplished by using a portion of the Power-up Timer. This PLL lock time-out, also known as TPLL, usually lasts for two milliseconds and comes after the oscillator start-up time-out (OST).

● Brown-out Reset (BOR)

The Brown-out Reset circuitry can be disabled (if the BOREN configuration bit is clear or has been programmed) or enabled (if the bit is set). The brown-out condition will reset the chip if the value of VDD drops below parameter D005 for a value greater than parameter 35. If VDD drops below parameter D005 for a duration less than parameter 35, a RESET might not occur. Brown-out Reset will be the state that the chip is in until VDD is higher than BVDD. If the Power-up Timer is turned on, it will be activated as soon as VDD becomes higher than BVDD; after that, it will maintain the chip in RESET for an extended period of time delay (parameter 33). If VDD falls below BVDD while the Power-up Timer is operating, the chip will enter a Brown-out Reset, and the Power-up Timer will be initialized. This will occur if VDD drops below BVDD. The additional time delay will begin after the Power-up Timer detects VDD has increased farther than BVDD.

Time-out Sequence: The following sequence begins when the power is turned on: After the POR time delay has run its course, the first step is to trigger the PWRT time-out. After then, the OST is made active. The entire time-out will change depending on the setup of the oscillator and the current state of the PWRT. For instance, if you operate in RC mode and have the PWRT turned off, there will be no time-out. If the MCLR is kept low for a sufficient time, the time-outs will eventually expire because the POR pulse causes them. Increasing the MCLR value will start the execution process immediately. This can be handy for testing and synchronizing multiple PIC18FXXX devices that are working in parallel.


In conclusion, if you want to centralize your components to one device, the PIC18F252-I/SP microcontroller manufactured by Microchip Technology is a great option. This microcontroller can handle many applications with its wide temperature range, fast clock speed, and high ADC resolution. Its typical operating supply voltage of 5V and flash program memory of 32KB make it a reliable and efficient choice for electronic designs. And, if you’re looking for high-quality electronic components, ICRFQ is a great resource to explore. Contact them today to learn more about the PIC18F252-I/SP and other electronic components that can take your designs to the next level.

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