27C512 - 512Kbit (64K x 8) UV/OTP EPROM | STMicroelectronics
MPN: 27C512 β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.2 | $5.20 |
| 10 | $4.68 | $46.80 |
| 100 | $4.16 | $416.00 |
| 500 | $3.64 | $1,820.00 |
| 1,000 | $3.12 | $3,120.00 |
27C512 Overview
An EPROM (Erasable Programmable Read-Only Memory) is a non-volatile semiconductor memory that retains firmware without power. Programmed electrically and erased only by exposure to UV light (in the UV variant) or not at all (OTP variant), the EPROM sits within the broader memory hierarchy of read-only memories that preceded EEPROM and Flash, and it remains a staple of legacy embedded systems, retro computing, and automotive engine controllers.
Key features include 512 Kbit density organized as 64K words by 8 bits, fast byte access (as fast as 45 ns on premium speed grades, per Atmel/Microchip equivalents), and a typical CMOS standby current of only 20 uA, which suits battery-backed and low-power legacy designs. The device supports 100% Flashrite programming for fast programming cycles and a JEDEC-standard pinout that allows drop-in interchange across manufacturers.
Architecturally, the 27C512 uses a CMOS cell array with parallel address decoding: 15 address lines (A0-A14), 8 bidirectional I/O data lines, and separate active-low Chip Enable (/E) and Output Enable (/G) controls, giving designers full bus control for memory-mapped systems. Program mode applies VPP on the /G or /E pin per the manufacturer datasheet.
Typical applications include firmware storage in 8-bit microprocessor systems, retro computer and arcade board restoration (Atari, pinball machines, engine ECUs), embedded BIOS replacement, and industrial control boards still in service.
Design consideration: verify programming algorithm and VPP requirements per the exact manufacturer datasheet before programming, as programming voltage and algorithm differ between ST, Atmel/Microchip, and Winbond variants.
This page synthesizes cross-brand drop-in alternatives, comparison tables, and legacy-sourcing guidance not found in any single manufacturer datasheet.
Drop-in alternatives for 27C512 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
M27C512-12F1
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
AT27C512R-70PU
β Drop-Inπ Reference alternative (not in catalog)
27C512A-90/P
β Drop-Inπ Reference alternative (not in catalog)
SST27SF512
β Drop-Inπ Reference alternative (not in catalog)
W27C512-45
β Drop-Inπ Reference alternative (not in catalog)
W27E512-45
β Drop-Inπ Reference alternative (not in catalog)
27C512 Maximum Ratings & Electrical Characteristics
| Memory Type | UV EPROM and OTP EPROM |
| Density | 512 Kbit |
| Organization | 64K x 8 |
| Supply Voltage (Read) | 5 V +/- 10% |
| Standby Current | 20 uA typical (CMOS standby) |
| Technology | CMOS EPROM |
| Programming | 100% Flashrite programming |
| Address Lines | A0 - A14 (15 lines) |
| Data Lines | D0 - D7 (8 lines) |
| Control Pins | /E (Chip Enable), /G (Output Enable) |
| Pinout Standard | JEDEC-approved 28-pin EPROM pinout |
| Package | DIP-28 (PDIP or CDIP windowed for UV) |
| Mounting Type | Through-Hole |
| Lifecycle Status | Obsolete; available from Rochester Electronics and stock distributors |
27C512 Pin Configuration
| Pin 1 | A15 β Address input, MSB |
| Pin 2 | A12 β Address input |
| Pin 3 | A7 β Address input |
| Pin 4 | A6 β Address input |
| Pin 5 | A5 β Address input |
| Pin 6 | A4 β Address input |
| Pin 7 | A3 β Address input |
| Pin 8 | A2 β Address input |
| Pin 9 | A1 β Address input |
| Pin 10 | A0 β Address input, LSB |
| Pin 11 | D0 β Data output, LSB |
| Pin 12 | D1 β Data output |
| Pin 13 | D2 β Data output |
| Pin 14 | GND β Ground |
| Pin 15 | D3 β Data output |
| Pin 16 | D4 β Data output |
| Pin 17 | D5 β Data output |
| Pin 18 | D6 β Data output |
| Pin 19 | D7 β Data output, MSB |
| Pin 20 | /E β Chip Enable (active low); VPP in program mode |
| Pin 21 | A10 β Address input |
| Pin 22 | /G β Output Enable (active low); /OE-VPP in program mode |
| Pin 23 | A11 β Address input |
| Pin 24 | A9 β Address input; electronic signature mode in program |
| Pin 25 | A8 β Address input |
| Pin 26 | A13 β Address input |
| Pin 27 | A14 β Address input; /PGM in program mode |
| Pin 28 | VCC β Power supply, 5 V |
Typical Applications
27C512 is suitable for 6 applications: Retro Computer and Arcade Board Restoration, Automotive Engine Controller (ECU) Firmware, Industrial Control and PLC Legacy Maintenance, Embedded BIOS and Firmware Storage, Telecom and Networking Line Card Firmware, Security and Access Control Systems.
Retro Computer and Arcade Board Restoration
The 27C512 is a primary firmware device in 1980s-1990s retro computers, arcade game boards, and pinball machines, and remains the standard replacement part for restoration work. Its JEDEC 28-pin DIP pinout plugs directly into the original sockets, and the 5V +/-10% supply matches period TTL logic without level shifting. The OTP plastic version offers an economical path for read-only firmware replacement, while the UV windowed ceramic version supports iterative development with UV erasure. Community resources such as RE-PROM adapters and Willem/TL866 programmers support standard 27C512 programming. Restorers should verify the exact speed grade when replacing in systems with tight access-time margins, as original boards may expect 150 ns or faster devices.
Recommended
Automotive Engine Controller (ECU) Firmware
Many automotive ECUs from the late 1980s and 1990s store calibration maps and firmware in 27C512-class EPROMs. The device's 512 Kbit density, 64K x 8 organization, and single 5V read supply make it a direct-fit replacement when re-chipping ECUs with performance or repair calibrations. The 28-pin DIP package fits the factory socket without adapters, and community tuning ecosystems (TunerCat and similar) are built around 27C512/27C128 programming. Because OTP devices cannot be revised, tuners commonly keep spare blank chips on hand or use re-programmable flash-based drop-ins like SST27SF512. Always use a programmer qualified for the specific chip's EPROM algorithm to avoid damage, and verify checksums after programming.
Recommended
Industrial Control and PLC Legacy Maintenance
Industrial controllers, motor drives, and I/O boards designed around 8-bit microprocessors frequently store firmware in 27C512 EPROMs, and these systems often remain in service for decades. The 27C512 provides maintenance engineers an authorized continued-source option via Rochester Electronics, alongside pin-compatible Microchip and Winbond equivalents. Its 20 uA typical CMOS standby current suits battery-backed equipment, and the industrial temperature ranges available on ceramic grades fit harsh factory environments. When a factory floor board fails, replacing the OTP EPROM with a freshly programmed device restores operation without PCB rework. Engineers should document the chip speed grade and programming checksum in spare-parts records to guarantee drop-in repeatability across future repairs.
Recommended
Embedded BIOS and Firmware Storage
The 27C512 historically served as BIOS and monitor firmware storage in single-board computers, embedded x86 platforms, and evaluation systems. In read mode it requires only a single 5V supply and presents standard EPROM read timing (address setup to data valid within the selected access time), letting designers replace older 27C256 parts by strapping the added A14 address line low. Separate /E and /G control pins enable clean bus interfacing and low-power deselection in memory-mapped designs. Today the part is used to repair or reproduce vintage SBCs and BIOS images; for new designs, Flash is recommended, but for faithful board restorations a genuine EPROM preserves original programming and timing behavior exactly as designed by the OEM.
Recommended
Telecom and Networking Line Card Firmware
Legacy telecom racks, modems, and networking line cards from the 1990s store boot code and configuration constants in 27C512 EPROMs. The JEDEC-standard 28-pin pinout means a programmed replacement can be swapped in the field without adapter boards, minimizing downtime on critical infrastructure. The device's deterministic read timing and non-volatile storage are well suited to boot-code roles where startup code must execute before any other memory is initialized. Spare socketed OTP EPROMs remain a practical field-service strategy: technicians carry pre-programmed spares and replace failed chips in minutes. When procuring spares, the Rochester Electronics 27C512-75DC CDIP-28 provides a qualified, traceable continued-production source for regulated telecom environments.
Recommended
Security and Access Control Systems
Access control panels, alarm systems, and surveillance controllers of the 27C512 era store authorization tables and operating firmware in socketed EPROMs. The part's non-volatility ensures that security data survives power loss without battery backup, and its 20 uA typical standby current suits mains-failure-battery-operated panels. Replacement strategy mirrors other legacy work: read the original device with an EPROM programmer, patch the configuration, and burn a fresh OTP device or use a flash-based drop-in for future editability. Installers should choose industrial temperature grades for outdoor enclosures and verify the read access time is at least as fast as the original device so the host processor's memory timing remains valid across the full temperature range.
Recommended
Recommended Products Summary
Engineering reference data for 27C512 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | M27C512-12F1 | AT27C512R-70PU | SST27SF512 | W27E512-45 |
|---|---|---|---|---|---|
| Package | DIP-28 (PDIP/CDIP) | DIP-28 - same | DIP-28 - same | DIP-28 - same | DIP-28 - same |
| Brand | STMicroelectronics | STMicroelectronics | Microchip Technology (Atmel) | Microchip Technology (SST) | Winbond Electronics |
| Density / Organization | 512 Kbit, 64K x 8 | 512 Kbit, 64K x 8 | 512 Kbit, 64K x 8 | 512 Kbit, 64K x 8 | 512 Kbit, 64K x 8 |
| Access Time | 90-150 ns (typical ST grades) | 120 ns | 70 ns | 70 ns | 45 ns |
| Supply Voltage (Read) | 5 V +/- 10% | 5 V +/- 10% | 5 V (single supply) | 5 V | 5 V |
| Technology | CMOS EPROM (UV/OTP) | CMOS EPROM (OTP) | CMOS OTP EPROM | Flash (electrically erasable) | EEPROM (electrically erasable) |
| Erasability | UV erase (windowed) or none (OTP) | None (OTP) | None (OTP) | Electrical (flash) | Electrical (EEPROM) |
| Lifecycle | Obsolete (Rochester continued) | Obsolete (Rochester continued) | Active production | Legacy stock | Legacy stock |
Key Differentiators
- Genuine EPROM technology with UV-erase option (vs SST27SF512)
- Faster access times available (vs M27C512-12F1)
- Wider temperature range equivalent exists (vs W27C512-45)
Design Notes
Programming algorithm compatibility is the most common failure point when mixing 27C512 vendors. ST, Atmel/Microchip, SST, and Winbond devices use different programming voltage (VPP) and algorithm requirements; using the wrong algorithm can damage the device or yield unreliable writes. Always select the exact manufacturer in your EPROM programmer software and verify the programmed image with a full-device checksum read before releasing the board. OTP parts cannot be corrected after programming - keep spare blanks.
The 27C512 is a through-hole DIP-28 device; design the PCB land pattern for a standard 0.6-inch (15.24 mm) row-spacing 28-pin DIP socket. Use a socket rather than soldering the EPROM directly so firmware can be updated or replaced without desoldering. Decouple VCC with a 100 nF ceramic capacitor placed within 10 mm of pin 28, and route the /E and /G lines short and direct to minimize address-to-data output-enable timing skew on fast (45-70 ns) speed grades.
In read mode the device runs from a single 5 V +/-10% rail with typical CMOS standby current of 20 uA when deselected, so bus-held /E high gives near-zero static drain in battery-backed systems. Active read current scales with access frequency and speed grade - faster grades draw more current per access. For power-sensitive legacy designs, gate /E with a chip-select decoder so the EPROM is deselected between accesses; this alone can reduce average system consumption measurably in polled memory maps.
Compliance Information
Legacy device predating RoHS; exemption status varies by manufacturer and production date. Compliance data not present in provided web sources.
