Teensy 4 Flash operating frequency and dummy cycles

PetervdPerk

New member
I was trying to determine the operating frequency of the Teensy 4 QSPI flash.

Looking at the code I've found the following.
deviceType - 1 - Serial Nor
sflashPadType - 4 - Quad Pads
serialClkFreq - 8 - 133Mhz
lutCustomSeqEnable - 0x0

So it seems that the Flash is running @ 133Mhz

LUT Read operation
0x0A1804EB, // lookupTable[0] 0x80
0x26043206, // lookupTable[1]

0x0A1804EB
CMD_SDR, 0xeb, 1PAD
RADDR_SDR, 0x18, 4PAD

0x26043206
DUMMY_SDR, 0x06, 4PAD
READ_SDR, 0x04, 4PAD

But after decoding the LUT tables I noticed that the DUMMY_SDR is 0x06.

Teensy 4.0 winbond_w25q16jvuxim states the following

1717270312200.png


Looking at the Teensy 4.1 winbond_w25q64jvxgim documentation it states the following.

1717269440764.png

If we want to operate the Teensy 4.1 @ 133Mhz it seems we need to have 8 dummy cycles, I think Teensy 4.0 is fine though.
I couldn't find any other reference but can anyone confirm the Teensy QSPI now running at 133Mhz with 6 dummy cycles or could it be something different?
 
Last edited:
The section you're referring to is for a QPI read, but the flash chip isn't in QPI mode. Instead it uses "Fast Read Quad I/O Instruction":
t4_nor_read.png

The M7-M0 bits aren't used so there's 6 dummy cycles total.
 
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