TUSB3200 datasheet(56/93 Pages) TI

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A–8

A.4.3

USB Out Endpoint Configuration Bytes

This section describes the individual bytes in the USB endpoint configuration blocks for the out endpoints. A set of

8 bytes is used for the control and operation of each USB out endpoint. In addition to the USB control endpoint, the

TUSB3200 supports up to a total of seven out endpoints.

A.4.3.1 USB Out Endpoint – Y Buffer Data Count Byte (OEPDCNTYx)

The USB out endpoint Y buffer data count byte contains the 7-bit value used to specify the amount of data received

in a data packet from the host PC. The no acknowledge status bit is also contained in this byte.

Bit

Mnemonic

NACK

DCNTY6

DCNTY5

DCNTY4

DCNTY3

DCNTY2

DCNTY1

DCNTY0

Type

R/W

BIT

MNEMONIC

NAME

DESCRIPTION

NACK

No acknowledge

The no acknowledge status bit is set to a 1 by the UBM at the end of a successful USB out

transaction to this endpoint to indicate that the USB endpoint Y buffer contains a valid data

packet and that the Y buffer data count value is valid. For control, interrupt, or bulk end-

points, when this bit is set to a 1, all subsequent transactions to the endpoint will result in a

NACK handshake response to the host PC. Also for control, interrupt, and bulk endpoints,

to enable this endpoint to receive another data packet from the host PC, this bit must be

cleared to a 0 by the MCU. For isochronous endpoints, a NACK handshake response to the

host PC is not allowed. Therefore, the UBM ignores this bit in reference to receiving the next

data packet. However, the MCU or DMA should clear this bit before reading the data packet

from the buffer.

6:0

DCNTY(6:0)

Y Buffer data count

The Y buffer data count value is set by the UBM when a new data packet is written to the Y

buffer for the out endpoint. The 7-bit value is set to the number of bytes in the data packet for

control, interrupt or bulk endpoint transfers and is set to the number of samples in the data

packet for isochronous endpoint transfers. To determine the number of samples in the data

packet for isochronous transfers, the bytes per sample value in the configuration byte is

used. The data count value is read by the MCU or DMA to obtain the data packet size.

A.4.3.2 USB Out Endpoint – Y Buffer Base Address Byte (OEPBBAYx)

The USB out endpoint Y buffer base address byte contains the 8-bit value used to specify the base memory location

for the Y data buffer for a particular USB out endpoint.

Bit

Mnemonic

BBAY10

BBAY9

BBAY8

BBAY7

BBAY6

BBAY5

BBAY4

BBAY3

Type

R/W

BIT

MNEMONIC

NAME

DESCRIPTION

7:0

BBAY(10:3)

Y Buffer base address

The Y buffer base address value is set by the MCU to program the base address

location in memory to be used for the Y data buffer. A total of 11 bits is used to specify

the base address location. This byte specifies the most significant 8 bits of the

address. All 0s are used by the hardware for the three least significant bits.

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