PIC32MX440F256H-80I Datasheet, PDF (286/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

PIC32MX3XX/4XX
FIGURE 11-4:
USB BUFFER DESCRIPTOR FORMAT: HARDWARE → SOFTWARE
Address Offset +0
31
26 25
16 15
—
BYTE COUNT<9:0>
—
876543210
PID<3:0> ^—
Address Offset +4
31
0
BUFFER ADDRESS<31:0>
Address Offset +0
bit 25-16 BYTE_COUNT<9:0>: Byte Count bits
Byte count reflects the actual number of bytes received or transmitted.
bit 7
UOWN: USB Own bit
1 = USB module owns the BD and its corresponding buffer
CPU must not modify the BD or the buffer.
0 = CPU owns the BD and its corresponding buffer
Note: This bit can be programmed by either the CPU or the USB module, and it must be initialized by the
user to the desired value prior to enabling the USB module.
bit 6
DATA0/1: Data Toggle Packet bit
1 = Data 1 packet received
0 = Data 0 packet received
Note: This bit is unchanged on an outgoing packet.
bit 5-2 PID<3:0>: Packet Identifier bits
The current token PID when a transfer completes.
The values written back are the token PID values from the USB specification: 0x1 for an OUT token, 0x9 for
an IN token or 0xd for a SETUP token.
In Host mode, this field is used to report the last returned PID or a transfer status indication.
The possible values returned are: 0x3 DATA0, 0xb DATA1, 0x2 ACK, 0xe STALL, 0xa NAK,
0x0 Bus Time-out, 0xf Data Error.
Address Offset +4
bit 31-0 BUFFER_ADDRESS: Buffer Address bits
Starting point address of the endpoint packet data buffer.
DS61143E-page 284
Preliminary
© 2008 Microchip Technology Inc.