MCXN94/54/53: USB embedded memory confusion Hello, I am trying to select the correct model of MCX N MCU to use for a new board design. In the datasheet MCXNP184M150F70.pdf, at page 12, below the models comparison table, there is the small NOTE 4 saying, "Dedicated USB RAM not available for devices which do not have USB FS module." I don't need the USB FS device. I need to use the USB HS device only. So I thought to save a bit of the BOM budget, selecting a model without the USB FS, such as the MCXN537, but the tone of the note 4 sounds important. I wanted to check the reference manual to get some light. Reference manual: MCXNP184M150F70RM.pdf Chapter 61, paragraph 61.7.1, page 2197 (about USB LS) says: "In addition to the address space occupied by the USBFS registers, 512 bytes of embedded RAM are required for use in Keep Alive mode. On this chip the starting address of the USB RAM block is 4801_0000h. You can use this USB RAM in Active power mode for BDT entries, USB data buffers, or other purposes." I suppose that is the RAM that note 4 of the datasheet is referring to. The following chapter, 62, about USB HS, never mentions the word "RAM." I am confused. Questions: 1. Why is it important to notice that models without USB LS don't have USB embedded RAM? 2. Can I still do ISP programming with the MCXN53 from an USB pendrive, using only the USB HS device and without the "USB embedded RAM"? Thank you so much to everybody! F. Board Design MCXN USB Re: MCXN94/54/53: USB embedded memory confusion Hi @elfarolab
The missing “dedicated USB RAM” does not prevent you from using USB HS on an MCXN537. The datasheet lists USB HS as present and USB FS as absent for that model; Note 4 says the dedicated RAM is absent with the USB FS module .
1. Why the note matters: It warns you not to count on that memory address or its USBFS Keep Alive function when selecting a part without USB FS. For a design using only USB HS, it is not, by itself, a disqualifier. Also, the module name here is USB FS (full-speed), not USB LS (low-speed).
2. ISP from a USB pendrive: Do not plan on the factory ROM doing that. NXP’s documented MCX N ISP programming path uses USB HID with a connected computer and a tool such as blhost , or one of the listed serial interfaces. A pendrive instead requires the MCU to act as a USB host , read mass storage, and program the image;
BR
Harry Re: MCXN94/54/53: USB embedded memory confusion thank you!
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