DSA communication protocol

1. DSA-Interface Specification

The DSA bus is an asynchronous and bidirectional communication bus designed internally for communication between a group of two microprocessors.

It has three bidirectional lines:

● Data-start synchronization and Data Transmission

● STB-data Election (data is valid when STB Is low)

● Ack-start synchronization, data transmission, confirmation and communication response

 

2. Communication instructions

Each data communication includes three phases:

● Start synchronous data transmission between the transmitter and receiver

● Data transmission transmits all data bits through data selection and response signals.

● The communication response receiver can let the transmitter know whether the communication is abnormal. If there is no error in the communication, it may be repeated until it is determined.

 

A processor is called a transmitter when it wants to transmit data. It transfers data from a synchronization phase and requests to receive the final communication response.

Other Processors automatically become receivers.

 

2.1 start Synchronization

The transmitter lowers the data line to let the other party know that it wants to send some data. Then it starts to wait until the ACK line is pulled down and receives a confirmation signal from the receiver, confirming that the transmission request is accepted and that the data is ready to be accepted.

Then the sender pulls the data signal and waits for the ACK line to be pulled up. If the Ack is pulled up, the synchronization is completed. Both the sender and receiver have prepared data transmission.

 

It is possible that the two processors need to transmit their data at the same time, simultaneously lowering the data line and then waiting for the ACK online response signal. Therefore, it is necessary to add timeout sending in the software at the beginning of synchronization. When the time-out period is exceeded, the servo processor and the servo processor pull the data line and then detect whether the user's processor initiates a synchronous signal. If yes, he will first accept the data, and then the servo processor will be able to pull down the data line and transmit the data again.

The servo processor cannot pass the synchronization phase when it has new data to be sent, the old data will be overwritten.

 

2.2 Data Transmission

All data bits in this part of the communication are transmitted from the transmitter to the receiver, and the data line is set to be sent according to the bitwise transmitter. When the data line becomes stable, the transmitter lowers the STB line to tell the receiver that the information on the data line is valid. When the low status of the STB line is identified, the receiver starts to read data first. The receiver then lowers the ACK line to tell the sender that the data has been read. When the sender detects that the Ack is low, it pulls the STB foot high. When the receiver detects that the STB is high, it pulls the ACK high and the complete 1-bit data ends.

If the servo processor cannot transmit 16-bit data in (ttrf), it pulls the high data line and the STB line, and pulls the ACK line to enter the Communication phase.

 

2.3 communication response

Peaks on the bus may cause synchronization between the transmitter and receiver. At this time, the receiver should have received the specified bit count accurately. If the receiver's bit counter is not equal to the specified count, the receiver clears the data line. Otherwise, the line remains high. After that, the receiver clears the STB line. This means that for the transmitter, the comparison result is valid on the data line. The transmitter reads the data line and sets the ACK line height. This means that the data line of the receiver is read by the transmitter. When the ACK line recognized by the receiver is high, it sets the data and STB line height of both. Now, all communications are completed and the communication is idle again on the DSA-bus. If no communication error occurs, the transmitter should repeat (only once) the last communication to start the synchronization phase.

If the receiver is not within the range of the tcom communication response phase to make an appropriate response, the servo processor (= TRANSMITTER) interprets this as a communication error and sets all rows of height.

 

When using this communication protocol, pay attention to the following points:

1. When the bus is idle, both the user processor and the servo processor are in the read data state. When one party needs to send data, it is set to write state.

2. In the synchronization or data transmission phase, if the timeout does not receive a corresponding response, the sender should convert the status to the read status. It is mainly used to process the data that both parties need to transmit at the same time.

3. The DSA bus is an asynchronous and bidirectional communication bus designed internally for communication between a group of two microprocessors. 4. Each bit transmitted must be synchronized. You can transmit only one bit at a time.

 

 

DSA communication protocol