PCF8563 RTC Chips, I2C Clock Modules and Boards

PCF8563 real-time clocks: select a bare IC, RTC module or complete system board

The PCF8563 family is used for calendar timekeeping in embedded equipment, portable instrumentation and microcontroller projects. This collection contains loose PCF8563T and PCF8563P clock chips, PCF8563-based I2C modules with supporting circuitry, and some larger assemblies whose product titles reference an onboard PCF8563. It also contains multi-model listings in which the selected option may be a different RTC or an unrelated component. The selected variant determines what ships. A listing titled PCF8563 is not a promise that every variant contains a PCF8563, a backup battery or a usable standalone clock board.

What a PCF8563 RTC does

A PCF8563 clock/calendar tracks seconds, minutes, hours, weekday, date, month and year independently of the host MCU's program timing. Its two-wire I2C interface lets a controller set and read time; clock-output, timer/alarm and interrupt functions depend on the actual chip configuration and the connections made available by the selected board. Calendar rollover and leap-year handling do not make the oscillator perfectly accurate: the installed 32.768 kHz crystal, loading, temperature, board design and calibration determine real-world drift. The PCF8563 is an RTC, not a general-purpose time server, temperature-compensated DS3231 replacement or nonvolatile file-storage device.

Some PCF8563 module descriptions specify a 32.768 kHz crystal, SDA/SCL I2C pads, INT interrupt and CLKOUT (sometimes printed COT) output, and a coin-cell holder. Some quote selectable clock outputs including 32.768 kHz, 1,024 Hz, 32 Hz and 1 Hz. These are features to verify on the specific variant and assembled board, not an assurance that every module exposes the same pins or that a bare IC comes with a crystal, holder, headers or battery. The chip's applicable supply range and a module's VCC range can differ: several listings describe a chip-level 1.0–5.5 V range while their boards specify external 3.3–5 V or a nominal 3.3 V. Check the selected part's documentation and I2C pull-up arrangement before interfacing a host.

How the products in this collection differ

• Bare PCF8563T: loose SOP-8 surface-mount clock ICs appear in various 5-, 10-, 20- and larger piece options. A bare IC requires a suitable footprint, oscillator components, power arrangement and host interface. A package or seller title alone is not evidence that a board or coin cell is included.
• Bare PCF8563P and PCF8563TS: some variants specify PCF8563P DIP-8; others specify PCF8563TS in a smaller surface-mount package. Verify the exact manufacturer's package drawing and pin assignment before substituting one footprint for another. DIP-8, SOP-8 and MSOP-8 options are not mechanically interchangeable.
• PCF8563T RTC modules: various listings offer 1-, 5-, 10- or 25-board selections. Individual descriptions mention a crystal, I2C connections and sometimes battery holder or loose unsoldered pin headers. One ten-piece listing says headers are supplied but not soldered; several others explicitly say without battery. A holder is not proof that a CR2032 is in the package.
• Battery option and power-fail behavior: a particular module listing offers separate “with Batter” and “without bat” choices. Backup timekeeping depends on the selected board's power path, a suitable installed cell, its condition and the current draw. Do not treat a seller's ten-year battery-life assertion as a verified life guarantee. Confirm whether any module includes a charging path; do not insert a non-rechargeable coin cell into a circuit that charges the backup cell.
• Other RTC options: some multi-model pages offer DS1302, DS1307, DS3231, DS3231M, PCF8523, PCF8583 or PCF85163 instead of PCF8563. They differ in interface, oscillator arrangement, accuracy, pinout, battery handling and package. DS1302 uses a three-wire serial interface rather than the PCF8563 I2C interface. DS3231 is a different clock family with its own integrated oscillator architecture; “better than DS3231” in a PCF8563 module title is an unsupported universal performance comparison.
• Other ICs sharing a title: selectable PCF8591 ADC/DAC, PCF8574 or PCF8575 I/O expanders, PCA9515/PCA9517 I2C interface chips, power ICs and transistors are different functions. In a mixed listing each option refers to its own named model and pack quantity. The presence of PCF8563 text elsewhere in the title does not transform those chips into RTCs.
• Systems with an onboard RTC: ESP32-S3 RS485/Ethernet/PoE development boards, a KVM expansion board and T5 4.7-inch e-paper systems mention PCF8563 among many onboard functions. Those selected variants are complete boards or display assemblies, not shipments of loose RTC ICs. T5 options distinguish radio frequencies and, in one listing, GPS versions; verify the exact selection and region/application requirements.

Clock-module selection checklist

1. Identify the physical deliverable: bare IC, assembled RTC board, module with or without housing and cable, or complete host/display board. Check the option label and pack count, not just the headline.
2. Confirm the actual clock chip: a mixed-model RTC listing may put PCF8563 beside DS1302, DS1307, DS3231 and PCF8523. Choose the PCF8563 variant explicitly if that is the architecture your firmware targets.
3. Confirm supply and I2C levels: distinguish the clock silicon's limits from the assembled board's VCC recommendation. Verify the bus pull-up voltage, pins, MCU I/O tolerance, expected I2C address and whether other devices on the bus conflict. Do not assume a 3.3 V label on one board applies to every listing.
4. Check time retention: inspect whether a backup holder, battery, crystal and power switchover are actually included. A module sold without a cell will not retain time across a power loss solely because it has a holder. Battery type and polarity matter.
5. Check accuracy expectations: a low-power crystal RTC and a temperature-compensated RTC are not interchangeable accuracy classes. Do not borrow a DS3231 temperature or precision specification for a PCF8563 board. For an accuracy-critical design, consult the selected chip's manufacturer data and the board's oscillator implementation, then test drift under operating conditions.
6. Match packaging and assembly: DIP-8 versus surface-mount packages, unsoldered headers, housed versus bare modules and cable inclusion each change mechanical integration. Confirm dimensions and pin order for the purchased option.

Engineering details worth checking before layout or firmware

Read the selected PCF8563 device documentation for register mapping, oscillator status or voltage-low indication, time-setting sequence and interrupt-clearing behavior. A battery-backed clock can continue counting while the MCU is off, but the host must still initialize and validate stored time, especially after first power-up or backup depletion. A programmable output does not imply arbitrary waveform frequency, and an alarm/interrupt line is not a load-driving relay output. Where INT is open-drain, it needs an appropriate pull-up on the receiving side. I2C supports a bus architecture, but the actual voltage, pull-up values, line length and bus speed must be evaluated at board level. Some listings quote a 400 kHz interface figure; this is not a promise that every host-board wiring arrangement meets it.

Beware of source descriptions that blend technical claims from different chips. For example, a page advertising several RTC variants may describe DS3231's temperature-compensated oscillator, DS1302's three-wire interface and DS1307's RAM in one block. None of those functions should be automatically ascribed to a PCF8563 option. Likewise, an AT24C32 is a separate EEPROM, not a PCF8563 clock feature; if it is present on a selected module, 32 kilobits corresponds to approximately 4 kilobytes, not 32 kilobytes. Check whether that separate memory is actually populated.

Frequently asked questions

Is the PCF8563 a sensor that records data by itself? It is a clock/calendar IC. Some sellers use “time record sensor board” as a product label, but logging and storage require a host or additional memory and firmware.

Will every board keep time when power is removed? No. A suitable backup path and battery are required; some modules are explicitly sold without the battery. Inspect the selected option and board design.

Can I replace DS3231 with PCF8563 without changing the design? Do not assume so. Their oscillator implementations, electrical characteristics and software details differ, and even their assembled boards can have different wiring and battery arrangements.

Does PCF8563 in a development-board title mean loose chips ship too? No. The title may describe an onboard RTC within a complete ESP32, KVM or e-paper assembly. Select a bare-IC listing when you need loose parts.

Model references are used to help identify choices, not to certify original-manufacturer provenance, universal compatibility, tested clock drift, safety approvals or guaranteed battery life. Verify design-critical specifications against the exact selected part and its authoritative documentation.