STR720 datasheet(294/401 Pages) STMICROELECTRONICS

294 / 401 page

STR720 - USB SLAVE INTERFACE (USB)

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Bit 8

EP_KIND: Endpoint Kind

The meaning of this bit depends on the endpoint type configured by the

EP_TYPE bits. Table 64 summarizes the different meanings.

DBL_BUF: This bit is set by the software to enable the double-buffering

feature for this bulk endpoint. The usage of double-buffered bulk endpoints is

explained in “Double-Buffered Endpoints”.

STATUS_OUT: This bit is set by the software to indicate that a status out

transaction is expected: in this case all OUT transactions containing more

than zero data bytes are answered ‘STALL’ instead of ‘ACK’. This bit may be

used to improve the robustness of the application to protocol errors during

control transfers and its usage is intended for control endpoints only. When

STATUS_OUT is reset, OUT transactions can have any number of bytes, as

required.

Bit 7

CTR_TX: Correct Transfer for transmission

This bit is set by the hardware when an IN transaction is successfully

completed on this endpoint; the software can only clear this bit. If the CTRM

bit in the USB_CNTR register is set accordingly, a generic interrupt condition

is generated together with the endpoint related interrupt condition, which is

always activated.

Note

A transaction ended with a NAK or STALL handshake does not set

this bit, since no data is actually transferred, as in the case of

protocol errors or data toggle mismatches.

This bit is read/write but only ‘0’ can be written.

STR720 Datasheet(PDF) 294 Page - STMicroelectronics