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Serial Flash with/without WriteProtect and Hold Input
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fossil:
I was exploring 16MB flash for a custom ESP8266 board. I have come across flash chips which do not implement "write protect" and "hold" for "Dual SPI" mode.
For example
Winbond W25Q128FW implements WP and Hold.
Winbond W25Q128JV does not implement WP and Hold.
The ESP8266 reference designs use dual SPI mode with "write protect" and "hold".
Do I need to stick with the ones which implement WP and Hold?
Or, can I ignore the WP and Hold outputs of ESP8266 without any consequences?
Note: I have attached the excerpt from datasheet(s) showing features and pins.
nsrmagazin:
It depends on 2 problems:
0. The pins still might need to be connected to GND or VCC in order for the IC to function properly.
1. If the programming uses these 2 functions its bad. Otherwise you can freely disable them.
fossil:
--- Quote from: nsrmagazin on January 24, 2019, 06:32:04 pm ---It depends on 2 problems:
0. The pins still might need to be connected to GND or VCC in order for the IC to function properly.
1. If the programming uses these 2 functions its bad. Otherwise you can freely disable them.
--- End quote ---
I am trying to find out if ESP8266 uses these ping for programming. It seems ESP8266 allows one to select the SPI mode for programming flash. I will verify and update the thread.
fossil:
After some search on various ESP8266 forums, found the answer to my question.
The attached diagram shows how to wire the flash to be able to repurpose the GPIO9 and GPIO10, which answers my question.
The following paragraph is copied from the following link.
If you want to use GPIO9 and GPIO10 you must lift flash pins (3 - WP and 7 - HOLD) and pull up to VCC, then you can use these GPIOs (9&10). When flashing firmware (for example with Espressif Flash Tool) you must select DIO mode or change it manually in firmware.
If one wants to read the long answer here is the link to web archive as original site seems to be down.
https://web.archive.org/web/20180115033652/http://smarpl.com/content/esp8266-esp-201-module-freeing-gpio9-and-gpio10
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