
7532/7536 Group User’s Manual
APPLICATION
2-53
2.4 USB
(5)
Data structure
Data which composes the communication of USB transmits and receives data that the structure
number of bits is different as shown in Figure 2.4.2 continuously by the LSB first.
Basically, the contents except SYNC which is synchronizing signal and EOP which is the completion
signal are treated as data.
Accordingly, the difference of the number of bits can be detected by forecasting and determining the
following data from the content of PID.
Table 2.4.3 shows the content of data which composes the packet.
Table 2.4.3 Data structure of USB packet
Data name
Synchronize
Packet IDentifier
Frame Number
Address
ADDR
Endpoint
Data
Token CRCs
Data CRCs
End Of Packet
Note:
The DATA numbers in L.S. are shown in this table.
Symbol
Sync
PID
–
ENDP
DATA
CRC5
CRC16
EOP
Operation
Synchronized signal to communicate
Data indicating processing of packet
Data to control the frame during communication by time
Data to confirm the transmit destination of packet
and notify from transmitter
Data indicating transfer type used by device
Data to be used when the processing specified by
PID is executed
Data to check error when PID is token and SOF
Data to check error when PID is DATA
Data indicating the completion of packet
Structure
8 bits
8 bits
11 bits
7 bits
4 bits
8 bits
0 to 8 bytes
5 bits
16 bits
2 bits
PID is classified into 3 kinds in the structure data of Table 2.4.3.
Token is used to give the device the instruction of communication processing, and report on the
processing of the following stages. It is only a host to be able to issue the token.
Data is used to transmit and receive data which is the content of the instruction of the token, and
execute the processing in the stage. It is a host to be able to issue the data when the token is SETUP
and OUT, and it is a device when the token is IN.
Handshake indicates the completion of the communication at the end.
It is a host to be able to issue the handshake when the token is IN, and it is a host when the token
is SETUP and OUT.
Table 2.4.4 shows PID.
Table 2.4.4 PID
Packet
type
Token
Data
Handshake
Special
PID name
SETUP
IN
OUT
SOF
DATA0
DATA1
ACK
NAK
STALL
PRE
Processing
The processing is reported by host to device
Data transmit is requested from host to device
Data receive is requested from host to device
Top of frame is indicated by host to device
The state that sequence bit of transmit/receive data is even is indicated
The state that sequence bit of transmit/receive data is odd is indicated
Normal completion of communication is reported
The state that device is waiting for communication is reported
Completion error of communication is reported
Communication to the L.S. device which has low-priority is enabled
Bit structure
(bits 3 to 0)
1101
2
1001
2
0001
2
0101
2
0011
2
1011
2
0010
2
1010
2
1110
2
1100
2
In 7532/7536 Group, data except SOF and PRE of PID can be controlled by software.