27C256L-20R - 256Kbit 32Kx8 CMOS EPROM 200ns | WSI
N.º de pieza: 27C256L-20R ✗ Fin de vida| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $3.2 | $3,20 |
| 10 | $2.88 | $28,80 |
| 100 | $2.45 | $245,00 |
| 500 | $2.1 | $1.050,00 |
| 1.000 | $1.85 | $1.850,00 |
27C256L-20R Descripción general
An EPROM (Erasable Programmable Read-Only Memory) is a non-volatile semiconductor memory device that retains programmed data without power. Data is written electrically at programming time and can be erased only by exposure to ultraviolet light through the quartz window of the ceramic package. EPROMs sit in the memory hierarchy between mask ROM (fixed at fabrication) and EEPROM/Flash (electrically erasable), and are classified as Memory ICs within the broader integrated circuit family.
Key features of the 27C256 family include fast access-time speed options (as fast as 150 ns on faster grades; the -20 suffix denotes 200 ns), very low power consumption with 20 uA typical CMOS standby current on the L (low-power) variant, a JEDEC-approved 28-pin pinout, and single +5 V operation. The 100% Flashrite programming scheme allows typical programming times per byte to be minimized, speeding production programming throughput.
Architecturally, the device organizes 262,144 bits as 32,768 words of 8 bits each, addressed via 15 address lines (A0-A14) with eight bidirectional data lines (O0-O7). Control is provided by chip enable (CE), output enable (OE), and program (PGM/VPP) pins, allowing standard memory-bus interfacing and read operation with CMOS-level standby currents when deselected.
Typical applications include firmware and BIOS storage in legacy embedded systems, industrial control boards, automotive ECUs of the pre-Flash era, telecom equipment, and replacement/repair of obsolete ROM devices in service and maintenance scenarios.
When designing with this EPROM, respect the 200 ns access time when matching to microprocessor wait-state requirements, and provide proper VPP/PGM handling during in-system or off-board programming. Note that erasure requires a UV eraser, not electrical erasure.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Alternativas directas para 27C256L-20R — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con 27C256L-20R (mismo factor de forma y huella) — difiere en Memory Type, Package, Mounting Type, Organization, Memory Size.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
27C256L-20
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
27C256L-15
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
27C256T-20
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
27C256-20
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
27C256T-15/SO
✅ Sustitución directa✓ En stock
$1.9 / unidad
Ver hoja de datos →27C256L-20R Especificaciones
| Tamaño de memoria | 256 Kilobit |
| Organización de memoria | 32K x 8-bit |
| Tipo de memoria | CMOS EPROM (UV erasable) |
| Access Time | 200 ns (-20 speed grade) |
| Tensión de alimentación | Single +5 V with +/-10% tolerance |
| Standby Current | 20 uA typical (CMOS standby) |
| Programming Scheme | 100% Flashrite programming |
| Pinout | JEDEC-approved 28-pin pinout |
| Address Lines | A0 to A14 (15 lines) |
| Data Lines | O0 to O7 (8 lines) |
| Control Signals | CE, OE, PGM/VPP |
| Encapsulado | 28-pin package (per JEDEC EPROM pinout) |
| Tipo de montaje | Through-Hole |
| Erase Method | Ultraviolet light (UV EPROM) |
Configuración de pines de 27C256L-20R
| Pin 1 | VPP — Program supply voltage |
| Pin 2 | A12 — Address input |
| Pin 3 | A7 — Address input |
| Pin 4 | A6 — Address input |
| Pin 5 | A5 — Address input |
| Pin 6 | A4 — Address input |
| Pin 7 | A3 — Address input |
| Pin 8 | A2 — Address input |
| Pin 9 | A1 — Address input |
| Pin 10 | A0 — Address input |
| Pin 11 | O0 — Data output 0 |
| Pin 12 | O1 — Data output 1 |
| Pin 13 | O2 — Data output 2 |
| Pin 14 | GND — Ground |
| Pin 15 | O3 — Data output 3 |
| Pin 16 | O4 — Data output 4 |
| Pin 17 | O5 — Data output 5 |
| Pin 18 | O6 — Data output 6 |
| Pin 19 | O7 — Data output 7 |
| Pin 20 | CE — Chip enable |
| Pin 21 | A10 — Address input |
| Pin 22 | OE — Output enable |
| Pin 23 | A11 — Address input |
| Pin 24 | A9 — Address input |
| Pin 25 | A8 — Address input |
| Pin 26 | A13 — Address input |
| Pin 27 | PGM — Program enable |
| Pin 28 | VCC — Power supply (+5 V) |
Aplicaciones típicas
27C256L-20R es adecuado para 6 aplicacións: Legacy Firmware / BIOS Storage, Industrial Control Boards, Automotive ECU Repair (Legacy), Telecom Equipment, Obsolete Component Replacement / Repair, Embedded Systems Education and Prototyping.
Legacy Firmware / BIOS Storage
The 27C256L-20R stores boot firmware and BIOS code in legacy computer and embedded controller boards that use 28-pin EPROM sockets. Its 32K x 8 organization holds a full 32 KB BIOS image, and the 200 ns access time meets the timing of mid-1980s to 1990s microprocessors without wait states. Because the device is UV-erasable, service technicians can re-program firmware revisions on the same socket using the Flashrite programming scheme. For retrofit work, any 27C256-family part with -20 or faster speed grade is a pin-compatible substitute, preserving board-level layout and socket compatibility.
Recomendado
Industrial Control Boards
Industrial PLCs, motor controllers, and process-control boards of the pre-Flash era commonly used 27C256 EPROMs to hold ladder-logic interpreters and control firmware. The 27C256L-20R fits this role with its single +5 V supply and +/-10% tolerance, which tolerates industrial power rails without a regulator change, and its 20 uA typical CMOS standby current reduces draw in battery-backed or low-duty-cycle controllers. Maintenance teams benefit from UV reprogrammability when control logic must be revised without redesigning the PCB, making the part a standard spares item for aging factory equipment.
Recomendado
Automotive ECU Repair (Legacy)
Engine control units from the 1980s and early 1990s frequently carried a 28-pin EPROM holding fuel and ignition maps. The 27C256L-20R serves as a repair and re-mapping device: technicians erase the original calibration under UV light and program updated lookup tables with an EPROM programmer using the Flashrite algorithm. The 200 ns access time satisfies typical ECU processor bus timing, and the JEDEC pinout guarantees socket compatibility. Because the L variant draws only 20 uA typical standby, it is also appropriate for keep-alive memory roles where modest battery-backed retention matters.
Recomendado
Telecom Equipment
Line cards, PBX controllers, and modems of the EPROM era used 27C256 devices for protocol and configuration code. The 27C256L-20R provides byte-wide non-volatile storage with deterministic 200 ns read timing, important for processors without cache that fetch code directly from ROM. The +/-10% supply tolerance suits telecom -48 V-derived 5 V rails with switching ripple, and CMOS standby keeps board-level power within budget when the device is deselected. Its JEDEC pinout means a failed device can be replaced or re-programmed in the field without PCB modification.
Recomendado
Obsolete Component Replacement / Repair
Repair shops maintaining aging test instruments, arcade boards, medical devices, and avionics trainers routinely need a 32K x 8 EPROM to replace a failed or lost-program device. The 27C256L-20R is the canonical choice: its JEDEC-approved 28-pin pinout is shared across every 27C256 manufacturer variant, so a replacement programs and reads identically regardless of the original brand. The 100% Flashrite programming scheme minimizes bench programming time when building small batches of replacement ROMs. Keeping a stock of -20 or faster grades covers virtually every 32 KB socket encountered in service work.
Recomendado
Embedded Systems Education and Prototyping
The 27C256L-20R remains popular in university microprocessor labs and hobbyist retro-computing projects because it demonstrates fixed-memory fundamentals: address decoding across 15 address lines, CE/OE control timing, and UV erasure as a tangible view of non-volatile storage. With 200 ns access time and a single +5 V supply, it interfaces directly to classic 8-bit CPUs such as the Z80 and 6502 without glue-logic speed concerns. Students can erase, program, and re-run firmware cycles, building an intuitive understanding of memory-mapped code storage that Flash-based designs obscure.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para 27C256L-20R — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | 27C256L-20 | 27C256L-15 | 27C256T-20 | 27C256 |
|---|---|---|---|---|---|
| Package | 28-pin DIP (JEDEC EPROM) | 28-pin DIP (JEDEC EPROM) - same | 28-pin DIP (JEDEC EPROM) - same | 28-pin DIP (JEDEC EPROM) - same | 28-pin DIP (JEDEC EPROM) - same |
| Brand | WSI (WaferScale Integration) | WSI (WaferScale Integration) | WSI (WaferScale Integration) | WSI (WaferScale Integration) | Microchip Technology |
| Organization | 32K x 8-bit | 32K x 8-bit | 32K x 8-bit | 32K x 8-bit | 32K x 8-bit |
| Supply Voltage | Single +5 V +/-10% | Single +5 V +/-10% | Single +5 V +/-10% | Single +5 V +/-10% | Single +5 V +/-10% |
| Memory Size | 256 Kilobit | 256 Kilobit | 256 Kilobit | 256 Kilobit | 256 Kilobit |
Diferenciadores clave
- Low-power CMOS standby core (frente a 27C256-20)
- Cost-effective 200 ns speed grade (frente a 27C256L-15)
- Reel packaging for production runs (frente a 27C256L-20)
Notas de diseño
The 27C256L-20R operates from a single +5 V supply with a standard +/-10% tolerance (4.5 V to 5.5 V). Decouple VCC with a 0.1 uF ceramic capacitor close to pin 28 and pin 14 ground return. During programming, VPP (pin 1) must be raised to the programming voltage specified in the manufacturer datasheet - never leave VPP tied to a high voltage in read mode, as this can damage the device or corrupt contents. Estimated: with 20 uA typical CMOS standby current, battery-backed standby power is only about 0.1 mW at 5 V.
Verify the host processor bus timing against the 200 ns access time of the -20 grade. Access time is measured from address valid or from CE/OE falling edge - whichever constraint applies. If the processor cycle time minus address setup leaves less than 200 ns, insert a wait state or select a faster grade (27C256L-15 at 150 ns is pin-compatible). Unused address/data lines should follow standard CMOS practice; the eight outputs drive standard TTL/CMOS loads directly.
UV EPROMs are frequently damaged by programming with incorrect VPP levels or by erasing with an underpowered UV lamp. Use a calibrated programmer implementing the 100% Flashrite algorithm and confirm the quartz window is fully exposed during erasure - a partially covered window yields incomplete erase and intermittent bit errors that mimic device failure. Because WSI is defunct, authenticate broker-supplied parts: remarked or counterfeit 27C256 devices are common in the obsolete market. Mark programmed devices with an opaque label over the window to prevent sunlight-induced gradual data loss.
Información de cumplimiento
Compliance data not available in verified sources; WSI is defunct and this part is obsolete, so formal compliance documentation is generally unobtainable.
