SST27SF256 Flash Memory Reference
The SST27SF256 is an electrically-erasable CMOS flash memory chip serving as a direct, cost-effective replacement for the 27C256 EPROM in Honda ECU tuning applications.
The SST27SF256 is a 256 Kbit CMOS flash memory device. It serves as an electrically-erasable, high-performance replacement for the standard 27C256 EPROM used in various Honda ECU applications.
Technical Overview
Unlike traditional EPROMs that require ultraviolet (UV) light for erasure, the 27SF256 utilizes flash technology, allowing for rapid electrical erasure and reprogramming.
- Capacity: 256 Kbit (32K x 8)
- Compatibility: Pin-compatible with standard 27C256 EPROMs.
- Erasure: Electrical (Flash).
- Datasheet: SST27SF256 Datasheet (PDF)0
Tip
When sourcing components, search for the specific part number "SST27SF256" through authorized electronic component distributors to ensure genuine hardware.
Implementation Notes
The 27SF256 is widely used in ECU modification and chip tuning due to its ease of use compared to UV-erasable chips.
Important
Ensure your chip programmer supports the specific voltage and timing requirements for the SST27SF256 flash memory before attempting to write data.
Resistor Color Code Reference
Use the color bands on through-hole resistors to identify their resistance value before installing ECU jumpers, pull-ups, voltage dividers, or sensor-scaling parts.
How to Read the Bands
| Resistor Type | Band 1 | Band 2 | Band 3 | Band 4 | Band 5 |
|---|---|---|---|---|---|
| 4-band | 1st digit | 2nd digit | Multiplier | Tolerance | - |
| 5-band | 1st digit | 2nd digit | 3rd digit | Multiplier | Tolerance |
Color Values
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | x1 | - |
| Brown | 1 | x10 | +/- 1% |
| Red | 2 | x100 | +/- 2% |
| Orange | 3 | x1,000 | - |
| Yellow | 4 | x10,000 | - |
| Green | 5 | x100,000 | +/- 0.5% |
| Blue | 6 | x1,000,000 | +/- 0.25% |
| Violet | 7 | x10,000,000 | +/- 0.1% |
| Gray | 8 | x100,000,000 | +/- 0.05% |
| White | 9 | x1,000,000,000 | - |
| Gold | - | x0.1 | +/- 5% |
| Silver | - | x0.01 | +/- 10% |
| No band | - | - | +/- 20% |
Common ECU Examples
| Value | 4-Band Code | Typical Use |
|---|---|---|
| 220 ohm | Red, Red, Brown, Gold | LED/current-limiting or ECU hardware mods |
| 1k ohm | Brown, Black, Red, Gold | Pull-up, jumper, and driver-bias circuits |
| 1.2k ohm | Brown, Red, Red, Gold | Driver-bias circuits such as IACV repair references |
| 4.7k ohm | Yellow, Violet, Red, Gold | Transistor base resistor circuits |
| 10k ohm | Brown, Black, Orange, Gold | Pull-up, pull-down, and sensor-divider circuits |
Tip
Always confirm the measured value with a multimeter before soldering. Old ECU resistors can be heat-discolored, and some boards use small surface-mount parts marked with numeric codes instead of color bands.