Fairlight CVI, User Manual

Page: 203 / 283

RS232C PO RT CONTR O L
Baud rate
The rate at which the bits within a byte are sent is known as
the
Baud
rate. The transmi tting and recei ving devices must be set
to use the same baud ra te, otherwise the recei ver will not be able
to understand what is transmitted. In the CYI this can range
from ' 300 baud (300 bits per second) to 1 9200 baud. This can be
selected from the RS232 PORT CONTROL Men u to suit the
external computer. 9600 baud is the most common baud rate.
Parity
Parity can be used to check for errors in data transmission.
The CYI d oes' not check the parity of each byte it receives, but it
can be set to transmit any of the parity types
( E v e n , Odd, Space
or
None)
to suit the external computer.
Stop bits
After each byte, the transmitting device sends a n u mber of bits
which allow time for the system to settle down. These are known
as
Stop bi ts, and there will be either one or two of them. The
CYI can be set to expect and transmit ei ther one or two stop bits
using the RS232 PORT CONTROL Me nu. The use of two stop
bits is recommended where possi ble.
RS232C Signals
An RS232 connector will have up to six signal pins. Two are
data lines which operate as described a bove. The other four are
known as
handshake lines,
and they control the
flow
of data from
one device to another. The six possible signal pins on a device
are:
TXD - Transmit Data: Data from the de vice is transmitted
from this pin.
RXD - Receive Data:
Da ta is received from a nother device
through this pin.
RTS - Request to Send: A handshake
output
which is set to a
high level by the device when it is ready to be sent da ta. If the
device is 'busy' and does not wish to be sent data then it will
set RTS
low.
CTS - Clear to Send:
A handshake
input
which stops the device
from transmitting when it is held
low
by an external source.
DTR - Data Terminal Ready:
A
ha ndshake
output
with a
similar function to R TS.
DSR - Data Set Ready:
A
h a ndsh a k e
input
with a similar
function to CTS.
- SOFTWARE UPDATE