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APPLICATION
2.4 USB
7532/7536 Group User’s Manual
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Packet type
The host side controls all the communications in USB.
Basically, the host gives the device the instruction of the communication processing which the host
side executes (= Token), executes data transmit/receive (= Data), and indicates the completion of the
communication is shown at the end (= Handshake).
These communication processings are executed in order by each one unit which has the data
structure (= Packet format), and one processing (= Transaction) is completed.
The content of processing can be identified according to PID (Packet IDentifier field) which is one
unit of data (Field) which composes each packet.
Not only the content of processing, but also the data structure in the packet can be identified by this PID.
Table 2.4.2 shows the packet type of USB.
Table 2.4.2 Packet types of USB
Packet type
SOF (Start of Frame)
Token
Data
Handshake
Transmitter
Host
Host
Host/Device
Host/Device
Operation
Packet indicating the top of frame (1 ms) including all transfer types
Packet indicating the processing to execute
Packet indicating the transmit/receive data for processing shown by token
Packet indicating the result of communication processing
Fig. 2.4.2 Data structure of USB packet
In 7532/7536 Group, the PID, ADDR, ENDP and DATA of packet structure data in Figure 2.4.2 can
be controlled by software.
In 7532/7536 Group, the token, data, and the handshake of packet types in Table 2.4.2 can be
controlled by software.
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Packet structure
As for the packet type of USB, the data and the structure are different by PID.
Each packet includes the following data shown with PID for which the control is required by 7532/
7536 Group;
token: the receiver to communicate (ADDR) and transfer type (ENDP)
data: execution (DATA) of the processing ordered by the token
handshake: the completion of the communication
Figure 2.4.2 shows the data structure of the packet.
SOF
(Start Of Frame)
SYNC
8bits
8bits
PID
11bits
Frame Number
5bits
CRC5
Token
2bits
EOP
SYNC
8bits
8bits
PID
8bits
PID
8bits
PID
7bits
ADDR
5bits
CRC5
2bits
EOP
4bits
ENDP
Data
SYNC
8bits
8bits
0 to 8bytes
DATA
16bits
CRC16
2bits
EOP
Handshake
SYNC
8bits
2bits
EOP
Packet type
Notes 1:
The shaded parts show the data which requires processing by software in 7532 Group.
2:
The DATA number of data PID shows the number in L.S.
3:
Determination of “Start Of Frame” is not executed because the processing is not required.