13.22.2 Packet Format

Every internal driver status change will cause the driver to send a message to the host dsPIC DSC. The interface uses a standard UART baud rate of 9600 bits per second.

In the DE2 protocol, the transmitter and the receiver do not share a clock signal. A clock signal does not emanate from one transmitter to the other receiver. Due to this reason, the protocol is asynchronous. The protocol uses only one line to communicate, so the transmit/receive packet must be done in Half-Duplex mode. A new transmit message is allowed only when a complete packet has been transmitted and responded to.

The host must listen to the DE2 line in order to check for contentions. In case of contention, the host must release the line and wait for at least three packet length times before initiating a new transfer.

Figure 13-5 illustrates a basic DE2 data packet.