Panasonic FP2 User Manual page 10

Transmission Speed and Transmission Format
Start bit and Stop bit
With normal communication, it is rare for a data transmission to consist of a single data
element (character). Usually, characters of a certain unit are sent in succession. With
serial communication, one "0" bit is always inserted before each data element, to
separate the various data elements being transmitted, and a "1" is added at the end of
each data element, for the same purpose. The "0" inserted before the data is called a
"start bit" and the "1" added at the end of the data is called a "stop bit".
Stop bit "1"
0 1 0 1 0 0 0
One data element (character)
Start bit "0"
With the serial data unit, the start bits and stop bits are inserted automatically.
Stop bit length
With serial communication, one bit is normally used for the stop bit, but if there is a lot
of noise on the communication circuit, or if the transmission speed fluctuates sharply,
two bits can be used as the stop bit, to differentiate one data element from the next more
clearly.
When the stop bit is 1 bit
0 1 0 1 0 0 0
One data element (character)
Start bit
With the serial data unit, either "1 bit" or "2 bits" may be selected as the stop bit length.
viii
1 0 1 0 1 0 1
One data element (character)
Start bit "0"
Stop bit
1 0 1
Stop bit "1"
0 0 0 1 0 1 0
One data element (character)
When the stop bit is 2 bits
0 1 0 1 0
One data element (character)
Start bit
FP2 Serial Data Unit
Stop bit "1"
1 0 1 0 0 0 1
Start bit "0"
Stop bit
(when 2 bits
are used)
0 0 1 0 1 1
0 1