Attached are chip definitions for the PN25Fxx chips.
The PN25F08B is now frequently found in IoT devices, usually together with ESP8266, e.g. in Sonoff devices or the newer ESP-01 modules.
Chip seems to be functionally identical with many of the more common Winbond W25 ones.
Datasheet here: http://www.xtxtech.com/upfile/2016082517095182.pdf
The datasheet for the B variant is not easily available, it is assumed it is the "plain" version with a different manufacturer. (Vendor code 0x5E for B version vs 0xE0 for the "plain" one.) However, test on the B variant (in hand) with config based on the "plain" variant datasheet seem to give functional results.
PN24F08B is tested on a ch341a_spi programmer hardware (with a SOIC-8 clip and ESP-01 module). Identifies, reads, erases, writes.
(Read chip. Check visually, looks like stock ESP-01 firmware. Erase chip. Read chip, get all 0xFF. Write in the firmware read in the first step. Read chip. Get identical file as the first one. Should pass as a successful test.)
PN24F04..64 and PN24F04B..128B are untested (not at hand). They are believed to differ only in memory sizes.
Due to my current lack of deep familiarity with differences between individual chip flavors, some ".feature_bits" may be missing.
Someone more skilled and familiar with the FlashROM project may like to take over here.
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Thomas Shaddack