The PIC16F1933 opens Microchip’s LCD-driven 193x generation in a 28-pin body: 4096 words (7 KB) of flash, 256 bytes of SRAM, 256 bytes of EEPROM, twenty-five I/O lines, an eleven-channel 10-bit ADC, and an on-chip LCD driver that spans up to sixteen segments across four commons – sixty display pixels without a driver IC. Three enhanced CCP modules and two plain CCP cover the PWM work. Products built on it – panel meters, small thermostats, appliance displays – carry their personality in the segment table as much as in the code, and that is where a casual copy fails. Our unlock encrypted PIC16F1933 memory service recovers both arrays from hardware you own.

The segment table is the interface

What each of the sixteen segments means – which glyph, which decimal point, which annunciator – is decided by constants the firmware writes into the LCD registers, and behind those, a font map in flash. A clone with the right code and the wrong segment table shows plausible gibberish to the user. Recovery therefore captures the display-related constants explicitly and verifies them: the fixture drives the clone and donor through the same state sequence and compares rendered segments pixel for pixel. One hardware quirk is documented in every report: on the 28-pin members, the COM3 and SEG15 functions share a physical pin, so a four-mux display loses SEG15 – a detail that has explained more than one “missing digit” mystery after a board revision. The storage architecture beneath is in the microcontroller internal storage structure analysis reference.

Bias generation for the glass runs from an internal charge pump with an external capacitor, and the pump’s configuration – contrast trim, mux ratio, frame frequency – comes from constants in flash. Panels that look washed out after a clone replacement have usually lost the contrast trim word, so our report prints it beside the segment map. Where the product switches mux ratios between screens, the switching moment is exercised too, because a pump that recovers slowly shows as a brief flicker that survives every static test.

Contrast trim words, once recorded, also give the owner a baseline if the glass is ever replaced with a different vendor’s part.

Reading a protected 28-pin part

Code protect in the configuration words closes external reads of program flash, and data protect does the same for the 256-byte EEPROM; lifting either costs the bulk erase that empties the array, so the erase never enters the workflow. The job starts by reading the configuration words to learn the policy, then reads each region while it is still protected, hashing sector by sector and repeating until a second pass is identical. Because the LCD’s bias is set from flash constants, those display registers are treated as data to be captured, not decoration to be skipped. General bench mechanics are in the how the MCU memory works guide.

Metering habits

Panel-meter firmware on this die typically pairs a slow ADC scan with a persistent energy counter in EEPROM, and the counter format is undocumented – it is whatever the original author chose. Capturing the EEPROM is therefore not optional; a replacement with an empty counter resets the customer’s billing history, which is the kind of failure that outlives the hardware. Our verification includes a counter-continuity check: values carried into the clone must survive a power cycle identically.

Panel buttons on this die ride on interrupt-on-change pins, and the debounce windows are constants like everything else. The comparison replays a recorded button sequence – fast presses, slow presses, two at once – and compares the decoded events, which catches a debounce constant captured from the wrong sector without any analogue instrumentation at all, and without waiting for a field unit to miss a press.

Duplication and family

Each verified image is programmed into a fresh 28-pin blank with its EEPROM content restored, then read back individually, using the MCU flash EEPROM data cloning pipeline. The larger 96-segment sibling in a 40/44-pin body is covered on the PIC16F1934 MCU page, the 14 KB 28-pin variant on the PIC16F1936 source code recovery, and the non-display 152xx family on the PIC16F15255 firmware page.

Scope

Engagements are limited to parts you own or are cleared to service. Send the locked PIC16F1933 and you receive a verified image, the segment-map evidence, and a protection map – and note that the destructive erase is never part of the process.