27C256L-20R - 256Kbit 32Kx8 CMOS EPROM 200ns | WSI
Référence : 27C256L-20R ✗ Fin de vie| Qté | Prix unitaire | 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 Présentation
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.
Alternatives de remplacement direct pour 27C256L-20R — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Variantes de cette série
Modèles de la même série directement compatibles avec 27C256L-20R (même facteur de forme et même empreinte) — différant par Memory Type, Package, Mounting Type, Organization, Memory Size.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
27C256L-20
✅ Remplacement direct ⚠️ Spécifications non vérifiées📋 Alternative de référence (hors catalogue)
27C256L-15
✅ Remplacement direct ⚠️ Spécifications non vérifiées📋 Alternative de référence (hors catalogue)
27C256T-20
✅ Remplacement direct ⚠️ Spécifications non vérifiées📋 Alternative de référence (hors catalogue)
27C256-20
✅ Remplacement direct ⚠️ Spécifications non vérifiées📋 Alternative de référence (hors catalogue)
27C256T-15/SO
✅ Remplacement direct✓ En stock
$1.9 / unité
Voir la fiche technique →27C256L-20R Spécifications
| Taille de mémoire | 256 Kilobit |
| Organisation de la mémoire | 32K x 8-bit |
| Type de mémoire | CMOS EPROM (UV erasable) |
| Access Time | 200 ns (-20 speed grade) |
| Tension d'alimentation | 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 |
| Boîtier | 28-pin package (per JEDEC EPROM pinout) |
| Type de montage | Through-Hole |
| Erase Method | Ultraviolet light (UV EPROM) |
Configuration des broches de 27C256L-20R
| Broche 1 | VPP — Program supply voltage |
| Broche 2 | A12 — Address input |
| Broche 3 | A7 — Address input |
| Broche 4 | A6 — Address input |
| Broche 5 | A5 — Address input |
| Broche 6 | A4 — Address input |
| Broche 7 | A3 — Address input |
| Broche 8 | A2 — Address input |
| Broche 9 | A1 — Address input |
| Broche 10 | A0 — Address input |
| Broche 11 | O0 — Data output 0 |
| Broche 12 | O1 — Data output 1 |
| Broche 13 | O2 — Data output 2 |
| Broche 14 | GND — Ground |
| Broche 15 | O3 — Data output 3 |
| Broche 16 | O4 — Data output 4 |
| Broche 17 | O5 — Data output 5 |
| Broche 18 | O6 — Data output 6 |
| Broche 19 | O7 — Data output 7 |
| Broche 20 | CE — Chip enable |
| Broche 21 | A10 — Address input |
| Broche 22 | OE — Output enable |
| Broche 23 | A11 — Address input |
| Broche 24 | A9 — Address input |
| Broche 25 | A8 — Address input |
| Broche 26 | A13 — Address input |
| Broche 27 | PGM — Program enable |
| Broche 28 | VCC — Power supply (+5 V) |
Applications typiques
27C256L-20R convient pour 6 applications: 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.
Recommandé
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.
Recommandé
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.
Recommandé
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.
Recommandé
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.
Recommandé
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.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour 27C256L-20R — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | 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 |
Principaux différenciateurs
- Low-power CMOS standby core (vs 27C256-20)
- Cost-effective 200 ns speed grade (vs 27C256L-15)
- Reel packaging for production runs (vs 27C256L-20)
Notes de conception
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.
Informations de conformité
Compliance data not available in verified sources; WSI is defunct and this part is obsolete, so formal compliance documentation is generally unobtainable.
