I have Sofi SP8 programmer for serial flash memory, with ISP interface for In-System programming.
I want try it to read/write memory chip WINBOND 25Q32BVSIG-1246 on board, without desoldering.
Manual have notes about this, but it's not clear a few points: if use programmer to provide power supply for the chip (device is power off), how to connect WP and HOLD pins to VCC? ISP interface have VCC pin(#2) that need be connected to VCC pin of chip, so, additionally WP & HOLD pins on chip must be connected to ISP VCC pin too? Should I use some 1 to 3-pins male header adapter for this to split programmer VCC pin to 3 pins?
The other method is to use Power supply from target board (so device should be power on).
Which way is preferable?
Here is ISP programming description from programmer Manual.
Best Answer
First thing: WP and HOLD should be soft-tied each with a pull-up, as the part also uses these pins as DQ in 4-bit mode. Never hard-tie them.
Second thing: When programming in-system you will need to provide a way to make sure the host doesn't interfere with the SPI pins. Unfortunately, if you just have the host powered off, the host SoC I/O pins will pull down these pins due to their protection diodes. Provide a way to high-Z these pins, by holding reset or some other way, such as a transmission gate, jumper block, etc.
Third thing: You have another option to connect the programmer: a clip directly onto the chip (SOIC clip.) Then you don't need a header.