7643 datasheet(218/424 Pages) RENESAS

218 / 424 page

Rev.2.00

Aug 28, 2006

page 97 of 202

7643 Group

REJ09B0133-0200

APPLICATION

2.6 USB

Fig. 2.6.2 Packet type

Fig. 2.6.1 1 frame image

SOF

Audio mouse printer/scanner

1ms

SOF

Audio

printer/scanner

1ms

SOF

Audio

printer/scanner

1ms

Isochronous transfer

Interrupt transfer

Bulk transfer

mouse

SOF packet : indicates the packet of frame start that Host sends every 1 ms.

PID

8 bits

Frame number

8 bits

CRC5

5 bits

PID : SOF(0xA5)

Token packet : indicates the packet Host sends at transaction start.

PID

8 bits

ADDR

7 bits

ENDP

4 bits

PID : OUT(0xE1),IN(0x69),SETUP(0x2D)

CRC5

5 bits

Data packet : indicates the packet to transfer data.

PID

8 bits

DATA

0 to 1023 bytes

PID : DATA0(0xC3),DATA1(0x4B)

CRC16

16 bits

Handshake packet : indicates the packet in transaction to control the flow.

PID

8 bits

PID : ACK(0xD2),NAK(0xA5),STALL(0x1E)

The start of each packet is SOP.

The end of each packet is EOP.

(2)

Communication protocol

The host CPU does control all USB communications. Even when data is transmitted to the host

from the device, the transmission is executed after the host gives the device the right to use the

bus.

In order for the host to process multiple transfers simultaneously, each transfer is scheduled in

packet units within 1ms frame. The diagram below shows an image of one frame.

q Packet

A packet is the unit used by the host CPU or the device to secure use of the bus. In USB

communications, data is transmitted and received in packet units. A packet is a group of data

string (field) of some bits. It starts from a SYNC (synchronous data) field and continues to a PID

(Packet ID) field. Each type of packet can be identified by this PID field. The following is a list

of packet types.

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