Table 35-4. Buffer descriptor fields (continued)Field Description7OWNDetermines whether the processor or the USB-FS currently owns the buffer. Except when KEEP=1,the SIE hands ownership back to the processor after completing the token by clearing this bit.This must always be the last byte of the BD that the processor updates when it initializes a BD.0 The processor has exclusive access to the BD. The USB-FS ignores all other fields in the BD.1 USB-FS has exclusive access to the BD. After the BD has been assigned to the USB-FS, theprocessor should not change it in any way.6DATA0/1Defines whether a DATA0 field (DATA0/1=0) or a DATA1 (DATA0/1=1) field was transmitted orreceived. It is unchanged by the USB-FS.5KEEP/TOK_PID[3]Typically, this bit is 1 with ISO endpoints feeding a FIFO. The microprocessor is not informed that atoken has been processed, the data is simply transferred to or from the FIFO. When KEEP is set,normally the NINC bit is also set to prevent address increment.0 Bit 3 of the current token PID is written back to the BD by the USB-FS. Allows the USB-FS torelease the BD when a token has been processed.1 This bit is unchanged by the USB-FS. If the OWN bit also is set, the BD remains owned by theUSB-FS forever.4NINC/TOK_PID[2]No Increment (NINC)Disables the DMA engine address increment. This forces the DMA engine to read or write from thesame address. This is useful for endpoints when data needs to be read from or written to a singlelocation such as a FIFO. Typically this bit is set with the KEEP bit for ISO endpoints that areinterfacing to a FIFO.0 The USB-FS writes bit 2 of the current token PID to the BD.1 This bit is unchanged by the USB-FS.3DTS/TOK_PID[1]Setting this bit enables the USB-FS to perform Data Toggle Synchronization.• If KEEP=0, bit 1 of the current token PID is written back to the BD.• If KEEP=1, this bit is unchanged by the USB-FS.0 Data Toggle Synchronization is disabled.1 Enables the USB-FS to perform Data Toggle Synchronization.2BDT_STALLTOK_PID[0]Setting this bit causes the USB-FS to issue a STALL handshake if a token is received by the SIEthat would use the BDT in this location. The BDT is not consumed by the SIE (the owns bit remainsset and the rest of the BDT is unchanged) when a BDT-STALL bit is set.• If KEEP=0, bit 0 of the current token PID is written back to the BD.• If KEEP=1, this bit is unchanged by the USB-FS.0 No stall issued.1 The BDT is not consumed by the SIE (the OWN bit remains set and the rest of the BDT isunchanged).Table continues on the next page...Programmers interfaceKL25 Sub-Family Reference Manual, Rev. 3, September 2012618 Freescale Semiconductor, Inc.
