UM0290 datasheet(10/76 Pages) STMICROELECTRONICS

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STR7/STR9 USB firmware library

UM0290

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Double-buffered endpoint functions: To obtain high data transfer throughput in bulk

or isochronous modes, double-buffered mode has to be programmed.

In this operating mode some fields of the endpoint registers and buffer description table

cells have different meanings.

To ease the use of this feature, several functions have been developed.

SetEPDoubleBuff: An endpoint programmed to work in bulk mode can be set as

double-buffered by setting the EP-KIND bit. The function SetEPDoubleBuff()

accomplishes this task.

SetEPDoubleBuff :

void SetEPDoubleBuff(u8 bEpNum);

bEpNum = endpoint number

FreeUserBuffer: In double-buffered mode the endpoints become mono-directional and

buffer description table cells of the unused direction are applied to handle a second

buffer.

Addresses and counters must be handled in a different way. Rx and Tx Addresses and

counter cells become Buffer0 and Buffer1 cells. Functions dedicated to this operating

mode are provided for in the library.

During a bulk transfer the line fills one buffer while the other buffer is reserved to the

application. A user application has to process data before the arrival of bulk needing a

buffer. The buffer reserved to the application has to be freed in time.

To free the buffer in use from the application the FreeUserBuffer function is

provided:

FreeUserBuffer:

void FreeUserBuffer(u8 bEpNum, u8 bDir);

bEpNum = endpoint number

Double buffer addresses

These functions set or get the buffer address value in the buffer description table

for double buffered mode.

SetEPDblBuffAddr :

void SetEPDblBuffAddr(u8 bEpNum,u16

wBuf0Addr,u16 wBuf1Addr);

SetEPDblbuf0Addr :

void SetEPDblBuf0Addr(u8 bEpNum,u16 wBuf0Addr);

SetEPDblbuf1Addr :

void SetEPDblBuf1Addr(u8 bEpNum,u16 wBuf1Addr);

bEpNum = endpoint number

wBuf0Addr, wBuf1Addr = buffer addresses (expressed as PMA buffer

addresses)

GetEPDblBuf0Addr :

u16 GetEPDblBuf0Addr(u8 bEpNum);

GetEPDblbuf1Addr :

u16 GetEPDblBuf1Addr(u8 bEpNum);

bEpNum = endpoint number

return value :

buffer addresses

Double buffer counters

These functions set or get the buffer counter value in the buffer description table

for double buffered mode.

SetEPDblBuffCount

: void SetEPDblBuffCount(u8 bEpNum, u8 bDir, u16

wCount);

SetEPDblBuf0Count

: void SetEPDblBuf0Count(u8 bEpNum, u8 bDir, u16

wCount);

SetEPDblBuf1Count

: void SetEPDblBuf1Count(u8 bEpNum, u8 bDir, u16

UM0290 Datasheet(PDF) 10 Page - STMicroelectronics

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