SLES003A Datasheet

IC型号：
SLES003A
PDF描述：
Texas Instruments [USB Streaming Controller]
文件大小：
487.38KB
芯片厂家：
TI

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2. The host PC sends an OUT token packet followed by a data packet addressed to the OUT endpoint. If the

data is received without an error, the UBM writes the data to the endpoint buffer, updates the data count

value, toggles the toggle bit, sets the NACK bit to a 1, returns an ACK handshake to the host PC, and asserts

the endpoint interrupt.

3. The MCU services the interrupt and reads the data packet from the buffer. To read the data packet, the MCU

must first retrieve the data count value. After reading the data packet, the MCU clears the interrupt and

clears the NACK bit to allow the reception of the next data packet from the host PC.

4. If the NACK bit is set to 1 when the data packet is received, the UBM simply returns a NACK handshake

to the host PC. If the STALL bit is set to 1 when the data packet is received, the UBM simply returns a STALL

handshake to the host PC. If a CRC or bit stuff error occurs when the data packet is received, no handshake

is returned to the host PC.

NOTE:

In double buffer mode for bulk OUT transactions, the UBM selects between the X and

Y buffer based on the value of the toggle bit. If the toggle bit is a 0, the UBM writes the data

packet to the X buffer. If the toggle bit is a 1, the UBM writes the data packet to the Y buffer.

When a data packet is received, the MCU determines which buffer contains the data packet

by reading the toggle bit. However, when using double buffer mode, data packets may be

received and written to both the X and Y buffer before the MCU responds to the endpoint

interrupt. In this case, simply using the toggle bit to determine which buffer contains the data

packet does not work. Hence, in double buffer mode, the MCU reads the X buffer NACK bit,

the Y buffer NACK bit, and the toggle bit to determine the status of the buffers.

2.2.7.3.2 Bulk In Transaction Using MCU

The steps followed for a bulk in transaction are:

1. MCU initializes one of the IN endpoints as an IN bulk endpoint by programming the appropriate USB

endpoint configuration block. This entails programming the buffer size and buffer base address, selecting

the buffer mode, enabling the endpoint interrupt, initializing the toggle bit, enabling the endpoint and setting

the NACK bit.

2. The data packet to be sent to the host PC is written to the buffer by the MCU. The MCU also updates the

data count value then clears the NACK bit to a 0 to enable the data packet to be sent to the host PC.

3. The host PC sends an IN token packet addressed to the IN endpoint. After receiving the IN token, the UBM

transmits the data packet to the host PC. If the data packet is received without errors by the host PC, an

ACK handshake is returned. The UBM then toggles the toggle bit, sets the NACK bit to a 1, and asserts the

endpoint interrupt.

4. The MCU services the interrupt and prepares to send the next data packet to the host PC.

5. If the NACK bit is set to 1 when the in token packet is received, the UBM simply returns a NAK handshake

to the host PC. If the STALL bit is set to 1 when the IN token packet is received, the UBM simply returns

a STALL handshake to the host PC. If no handshake packet is received from the host PC, the UBM prepares

to retransmit the same data packet again.

NOTE:

In double buffer mode for bulk IN transactions, the UBM selects between the X and Y

buffer based on the value of the toggle bit. If the toggle bit is a 0, the UBM reads the data packet

from the X buffer. If the toggle bit is a 1, the UBM reads the data packet from the Y buffer.

2.2.7.3.3 Bulk Out Transaction Through DMA

This transaction is used by mass storage class USB applications to move bulk data to an external device via the

TAS1020A DMA resources. The difference between MCU-supported bulk transactions and DMA-supported bulk

transactions lies in how the data in the assigned out endpoint buffer is distributed to its final destination. Two modes

of DMA operation are possible. One mode is a software handshake mode utilizing synchronization communication

between the MCU, the USB Buffer Manager (UBM), and an external device. The second mode is a direct exchange

mode that bypasses communication with the MCU and directly outputs USB packets to an external device via the

DMA resources. Higher bandwidth transactions can be achieved in the direct exchange mode.

2鈥?8

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