For example, suppose the host device is transmitting and receiving data from Port 1 and you wish to switch to Port 2.
1.Send
2.Wait two character times.
3.Read computer input buffer.
4.If there are no characters in the PC's input buffer, send ASCII 2. This will switch the PC to Port 2. If there are characters in the PC's input buffer, you may send ASCII 1 to continue communicating with Port 1 or ASCII 2 to switch to Port 2. Any characters received after sending the new port number will be from the new port.
The multiport does not start loading data from the new peripheral port into the host port I/O module until the new peripheral port number is received.
Mode of Operation 2 provides automatic message multiplexing between the host port and up to seventeen peripheral ports. Data received from the peripheral devices is treated as messages. A message begins when a peripheral port receives a character from the device connected to it. A message is completed when the message terminating character is received or when the buffer is full. Either condition will cause data to be transferred to the host device a message at a time, with the multiport inserting the peripheral port number prior to the actual message.
Messages will be sent automatically to the host device in a