Question about the FX2LP Endpoint Buffer

[Anonymous]

Dear all,

   

I two fundamental questions about architecture of EZ-USB FX2LP.

   

1. How many packets could be hold in a Quad Buffered Output Endpoint? (e.g. EP2).

   

- - This question arises while testing the Bulkloop example. The EP2 is configured as double buffered OUT. My first thought is that two consecutive "transfer data out" could be performed. But it turns out that 4 consecutive "transfer data out" could be performed before encountering error (code 997).

   

2. The RAM space for Endpoint 2, 4, 6, 8 Buffer is as large as 1024 bytes due to the TRM, then how is the quad buffered 512 bytes EP2 (or EP8) be implemented?

   

Please be so kind to share your knowledge. Thanks

[Hemanth]

You can make the EP2 quad buffered but not EP8. There are 12 valid buffer configurations which are mentioned in the TRM(Chapter 1: EZ_USB Endpoint Buffers section)

   

To change the buffer configuration use the EPXCFG register.

   

For example, to make EP2-OUT Quad buffered you need to do the following:

   

EP2CFG=0xA0;

   

Regards,

   

hman

[Anonymous]

Thank you hman! I resolved my question based on the TRM.