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M25P16 SPI flash memory + LPC1769 - prototype work great, designed PCB not so good...

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 18, 2016 by lpcware
Content originally posted in LPCWare by teslabox on Sun Apr 03 04:51:48 MST 2016
Hi everyone!

I need to use Micron M25P16 Serial Flash Embedded Memory with 16 Mb (2 MB) of space.
It communicates used SPI interface up to 75 MHz clock signal.

First I made a prototype universal PCB (one layer, THT, 2.54 mm raster/grid) with +3,30 DC V from my LPCXpresso LPC1769 Rev. C PCB
and pull-up 10 kOhm resistors at W# (not Write Protect) and HOLD# (not Hold) pins and pull-up 100 kOhm resistor at S# (not Chip Select)
and pull-down 100 kOhm resistor at C (serial Clock) according to the "Figure 5: Bus Master and Memory Devices on the SPI Bus"
on the page no 10 in the datasheet of Micron M25P16. Also I added serial 100 Ohm resistor at C (serial Clock) line to reduce generating noise from

this signal to the other lines of SPI interface (MOSI and MISO lines).

I connected the prototype PCB with M25P16 memory to the LPCXpresso LPC1769 using female-female universal pigtails (with ca. 20-25 cm long).
I wrote proper code in ANSI C according to the flash memory commands in the datasheet and it works proper up to 500 kHz of clock speed.

I use commands as follows:
- READ IDENTIFICATION,
- READ STATUS REGISTER,
- WRITE ENABLE,
- WRITE DISABLE,
- READ DATA BYTES,
- SECTOR ERASE
- PAGE PROGRAM.

On the beginning it is enough for me.
Everything works very good - no failures/error, every command it recognizable by memory and gives answer from it.
Also I prepared some ANSI C code with slower SPI clock 10 kHz, 25 kHz, 50 kHz, 100 kHz, 200 kHz - all of them works very good.



In next step I designed a PCB and after assembly all electronics parts it turned out that there are some troubles with communication with M25P16

flash memory. Sometimes it works properly some time not - something like memory does not recognize commends...? and gives no answer
I checked SPI lines with oscilloscope and the SPI lines during sending commands look quite good but there is no answer...
Lengths of SPI traces on the PCB are ca. 20-30 mm from LPCXpresso LPC1769 goldpin connectors and I used round corners routing pull-up and pull-down

resistors are the same, 100 Ohm serial resistor on serial Clock line is also the same, decoupling 100 nF/100 V + 1 uF/50 V MLCC ceramic resistors

on Vcc power pin are the same... Even I slow down clock speed up to only 10 kHz... no positive changes.
I use 2-layer PCB with 20 mils width of traces and 10 mils clearance between signal traces and GDN polygon and signal to signal traces.

Do you have any suggestions what I can check more or what I can do in this situation?
If you need more information from me I will write all them below.

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