Supporting USB - USB Mass Storage: Designing and Programming Devices and Embedded Hosts - page 41

Table 2-2: Bit functions for an endpoint's buffer descriptor status register when
the CPU owns the buffer descriptor.
Bit Name Description

7 UOWN 0 = the CPU owns the buffer descriptor and its buffer.

6 DTS Data toggle synchronization: 0 = DATA0, 1 = DATA1.

5 KEN Buffer descriptor keep enable:

0 = the SIE gives up ownership after processing a packet.
1 = the SIE keeps ownership when UOWN = 0 (use for SPP
configuration).

4 INCDIS Address increment disable:

0 = address increment enabled.
1 = address increment disabled (use for SPP configuration).

3 DTSEN Data toggle synchronization enable:

0 = accept packets with incorrect data toggle.
1 = ignore packets with incorrect data toggle.

2 BSTALL Buffer stall enable:

0 = don't return STALL handshake.
1 = return STALL handshake.

1 BC9 Byte count, bit 9.

0 BC8 Byte count, bit 8.

A BDT union can store the contents of the buffer descriptor's four registers:
typedef union _BDT
{
struct
{
BD_STAT Stat;

// status

byte Cnt; // byte count

byte ADRL; // buffer address, low byte

byte ADRH; // buffer sddress, high byte

};

struct
{
unsigned :8;
unsigned :8;
byte* ADR; // buffer address

};
} BDT;