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266 SA-1110 Developer’s Manual
Peripheral Control Module
• Special (not supported by the SA1110 UDC)
Token Packet
:
A Setup Token Packet consists of Sync, PID, Address, Endpoint, and CRC5 fields, as shown in
Figure 11-16. A Token Packet is placed at the beginning of a frame to identify OUT, IN, SOF, and
SETUP transactions. OUT and IN transactions are used to transfer data, the SOF transaction is
used to time isochronous transactions (not supported by the SA-1110 UDC), and the SETUP
transaction is used to control transfers for the configuration of Endpoints.
For OUT and SETUP transactions, the Address and Endpoint fields are used to select which
SA-1110 UDC Endpoint is to receive the data. For an IN transaction, the Address and Endpoint
fields are used to select which endpoint is to transmit data.
Figure 11-16. Setup Token Packet Format
Start–Of–Frame (SOF) is a special type of Token Packet that is issued by the Host once every
1-millisecond to time isochronous transactions (not supported by the SA-1110 UDC). The SOF
Token Packet consists of a Sync, PID, Frame Number (which is incremented after each frame is
transmitted), and CRC5 field, as shown in Figure 11-17.
Note: Even though the SA-1110 UDC does not make use of the Frame Number field, the presence of SOF
packets every 1-millisecond prevents the SA-1110 UDC from entering suspend mode.
Figure 11-17. SOF Token Packet Format
Data packet
:
A Data Packet consists of Sync, PID, Data (1 to 256 bytes), and CRC16 fields, as shown in the
Figure 11-18.
Data Packets follow Token Packets, and are used to transmit data between the Host and SA-1110
UDC. Two types of Data Packets (as specified by the PID) are:
• DATA0
• DATA1
DATA0 and DATA1 provide a mechanism to guarantee data sequence synchronization between the
transmitter and receiver across multiple transactions, i.e., the transmitter and receiver communicate
and agree which Data Packet type (DATA0 or DATA1) is to transmit first. For each subsequent
packet transmitted, the Data Packet type is toggled DATA0, DATA1, DATA0, and so on.
Figure 11-18. Data Packet Format
8 bits 8 bits 7 bits 4 bits 5 bits
Sync PID Address Endpoint CRC5
8 bits 8 bits 11 bits 5 bits
Sync PID Frame Number CRC5
8bits 8bits 0–256 bytes 16 bits
Sync PID Data CRC16