ML60852A Ver la hoja de datos (PDF) - Oki Electric Industry

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componentes Descripción

Fabricante

ML60852A

USB Device Controller

Oki Electric Industry 

1Semiconductor

FEDL60852A-03

ML60852A

(6) Data packet transmission and reception procedure during isochronous transfer mode

Transfer of data is the major function in the isochronous transfermode. When carrying out isochronous transfer

between the ML60852A and the host, the following packet communications are carried out via the USB bus for the

data transfer of each packet.

(a) Token packet transfer (IN token or OUT token) from the host to the ML60852A.

(b) Data packet transfer in the desired direction (from the host to the device or from the device to the host).

In the isochronous transfer mode, there is no handshaking that reports whether or not the packet transfer was

done normally.

The ML60852A requests the local MCU to send or receive packet data by asserting the INTR pin. The

interrupt cause is SOF. Upon receiving this interrupt, the local MCU writes the packet data into the transmit

FIFO of the EP set for transmission (ISO IN) in the isochronous transfer mode, or reads out data from the

receive FIFO of the EP set for reception (ISO OUT) in the isochronous transfer mode.

The above procedures of transferring one packet of data are explained below for transmission and reception

separately.

1) During transmission

The EP for ISO IN has a two-layer FIFO configuration. One FIFO is used for storing the packet data that is

written in by the MCU via the local bus. The other FIFO is used for transmitting the stored data to the USB bus

when an IN token is received. The roles of the two FIFOs are interchanged when an SOF packet is received.

Upon receiving an SOF interrupt, the local MCU writes the data to be transmitted during the next frame into the

corresponding transmit FIFO of the EP of the ML60852A. When the host transmits an IN token packet, the

ML60852A transmits to the host the packet data written in the transmit FIFO during the previous frame.

2) During reception

The EP for ISO OUT has a two-layer FIFO configuration. One FIFO is used for storing the packet data that is

output to the local bus when the MCU reads the received packet data. The other FIFO is used for storing the

packet data received from the USB bus. The roles of the two FIFOs are interchanged when an SOF packet is

received.

Upon receiving an SOF interrupt, the local MCU reads out the data that has been received during the previous

frame from the corresponding receive FIFO of the EP of the ML60852A. When the host transmits an OUT

token and a data packet to the ML60852A, the ML60852A stores that received data packet in the receive FIFO,

and that data packet is read out by the local MCU during the next frame.

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