TUSB3200 datasheet(59/93 Pages) TI

59 / 93 page

A–11

A.4.3.6.2 USB Out Endpoint – Isochronous Configuration Byte

This section defines the functionality of the bits in the USB out endpoint configuration byte for isochronous endpoints.

Bit

Mnemonic

OEPEN

ISO

OVF

BPS4

BPS3

BPS2

BPS1

BPS0

Type

R/W

BIT

MNEMONIC

NAME

DESCRIPTION

OEPEN

Endpoint enable

The endpoint enable bit is set to a 1 by the MCU to enable the out endpoint.

ISO

Isochronous endpoint

The isochronous endpoint bit is set to a 1 by the MCU to specify the use of a

particular out endpoint for isochronous transactions. This bit should be cleared to a 0

by the MCU for a particular out endpoint to be used for control, interrupt, or bulk

transactions.

OVF

Overflow

The overflow bit is set to a 1 by the UBM to indicate a buffer overflow condition has

occurred. This bit is used for diagnostic purposes only and is not used for normal

operation. This bit can only be cleared to a 0 by the MCU.

4:0

BPS(4:0)

Bytes per sample

The bytes per sample bits are used to define the number of bytes per isochronous

data sample. In other words, the total number of bytes in an entire audio CODEC

frame. For example, a PCM 16-bit stereo audio data sample consists of 4 bytes.

There are two bytes of left channel data and two bytes of right channel data. For a

four channel system using 16-bit data, the total number of bytes would be 8, which

would be the isochronous data sample size.

00h = 1 byte,

01h = 2 bytes,

…,

1Fh = 32 bytes

A.4.4

USB In Endpoint Configuration Bytes

This section describes the individual bytes in the USB endpoint configuration blocks for the in endpoints. A set of 8

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

TUSB3200 supports up to a total of seven in endpoints.

A.4.4.1 USB In Endpoint – Y Buffer Data Count Byte (IEPDCNTYx)

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

transmitted in a data packet to 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 in transaction to this endpoint to indicate that the USB endpoint Y buffer is

empty. For control, interrupt, or bulk endpoints, 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 transmit another data packet to 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 sending the next

data packet. However, the MCU or DMA should clear this bit after writing a data

packet to the buffer.

6:0

DCNTY(6:0)

Y Buffer data count

The Y buffer data count value is set by the MCU or DMA when a new data packet is

written to the Y buffer for the in 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.

TUSB3200 Datasheet(PDF) 59 Page - Texas Instruments

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