• SPI
  • Beginner
  • 5 min
  • JEDEC ID

Recipe · Beginner · SPI

How to read a SPI flash JEDEC ID

Before dumping a chip, ask it for its JEDEC ID. The SPI wiki documents the raw instruction [0x9F r:3] exactly for this kind of first probe.

Scan result over a bus or local network.
JEDEC ID is the fastest sanity check for CS, CLK, MOSI and MISO wiring.

Wiring View

Flash chip BP SPI CS#CS GPIOCLKSCK GPIODO / IO1MISO GPIODI / IO0MOSI GPIOGNDGNDVCCcorrect 3.3V su...
Generated from the wiring summary: Flash chip to BP SPI.
Step 1

Commands

Configure SPI pins, then send the JEDEC command as a raw instruction.

Result

What success looks like

A stable three-byte response means SPI wiring, chip select and MISO are working. The bytes identify the chip family and capacity; use them before choosing a dump/write workflow.

Troubleshooting

  • All FF FF FF: MISO floating, chip not selected, or chip not powered.
  • All 00 00 00: bus held low, wiring issue, or target board fighting the bus.
  • Response changes every run: poor clip contact or unstable power.
  • In-circuit flash may fail if the rest of the board drives the SPI bus.

Next steps

  • Use the SPI flash shell for probe, analyze, strings, read, dump or erase actions.
  • Use the Web SPI Flash Programmer or Flashrom adapter for a file backup.
  • Do not write until you have a verified backup.

SPI flash JEDEC ID FAQ

Why start with the JEDEC ID?

JEDEC ID is a small read-only transaction that proves SPI mode, chip select, clock, MOSI and MISO are plausible before you try probe, dump, erase or write workflows.

What should a healthy JEDEC response tell me?

A healthy JEDEC response gives a manufacturer ID, memory type and capacity code that stay consistent across repeated reads. It proves the basic SPI path is plausible, but it does not verify the flash contents.

When should I switch to the flash shell?

Use the flash shell once the three-byte ID is stable. It adds chip probing, content analysis, string search, byte reads, dumps and erase actions for SPI NOR devices.

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