ML60852 Ver la hoja de datos (PDF) - Oki Electric Industry

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componentes Descripción

Fabricante

ML60852

USB Device Controller

Oki Electric Industry 

1Semiconductor

PEDL60852-01

ML60852

(7) Packets and packet sizes

The ML60852 packs the transmit data into packets and unpacks (restores to the original form) the received data.

The packed data that is recognized by the software client is a set of data consisting of one or more packets, and this

is called an I/O request (IRP).

Among the several packets in an IRP, all the packets other than the last packet are transferred with the maximum

packet size. Only the last packet can be transferred as a "short packet", that is, a packet whose size is less than the

maximum packet size.

I/O Request Packet (IRP)

Packet

1

Packet

2

Packet

n-1

Packet

n

1 Packet

M Bytes

Maximum packet size

The ML60852 has payload registers corresponding to each end point, and it is possible to set the maximum packet

size for each end point in these registers. The maximum packet size should be within the capacity of the

corresponding FIFO, and can be set as follows:

(1) EP0 Receive packet size can be 32 bytes or less;

(2) EP0 Transmit packet size can be 32 bytes or less;

(3) EP1 Transmit/receive packet size can be 64 bytes or less;

(4) EP2 Transmit/receive packet size can be 64 bytes or less;

(5) EP3 Transmit/receive packet size can be 32 bytes or less;

(6) EP4 Bulk/interrupt transmit/receive packet size can be 64 bytes;

In the 5EP mode, the EP4 isochronous packet size can be 512 bytes or less;

In the 6EP mode, the EP4 isochronous packet size can be 256 bytes or less;

(7) In the 6EP mode, the EP5 bulk/interrupt packet size can be 64 bytes or less;

In the 6EP mode, the EP5 isochronous packet size can be 256 bytes or less.

On the USB bus, the separation between successive packets is distinguished by appending a special signal condition

called EOP (End of Packet) at the end of each packet. The appending of EOP during transmission and the detection

and removal of EOP during reception are carried out by the ML60852 automatically.

(1) At the time of transmission, the packet is deemed to have ended when the local MCU has completed writing the

required number of bytes of data in the transmit FIFO and has then asserted the transmit ready status bit. (The

actual addition of EOP is executed at the time of transmitting the data over the USB bus after waiting for the IN

token from the host.) The packet will be a short packet if the transmit packet ready status bit is asserted after

writing data with less number of bytes than the maximum packet size. In particular, by asserting the transmit

packet ready status bit without writing any data, it is possible to form a null packet whose data length is zero.

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