KATC-C1 Instructions Page 14 04/14
Other Features
Serial (RS-232C) Communications Port
The Knopp KATC-C1 Automatic Transformer Comparator includes a standard RS-232 Serial
Communications Port. This port can be used to send "Remote Commands" to the KATC-C1 from an
external computer. The port can also be used to transfer test result data from the KATC-C1 to the
computer. This chapter describes:
how to configure the port and your computer to establish communication,
remote commands which can be sent from the computer to the KATC-C1, and
the data output which is sent from the KATC-C1 to your computer.
Serial Port Configuration
The KATC-C1 Serial Port is configured as a "Data Set." This means that the KATC-C1 should be
directly connected to your computer through a standard RS-232 cable. A null modem is not required.
Pins used by the KATC-C1 are:
pin 2 ................. transmitted data (TD)
pin 4 ................. request to send (RTS)
pin 5 ................. clear to send (CTS)
pin 6 ................. data set ready (DSR)
pin 7 ................. signal ground (GND)
pin 8 ................. carrier detect (CD)
pin 20 ............... data terminal ready (DTR)
Under normal operation (the KATC-C1 is not trying to send data and is assuming Data Set configura-
tion), the TD, DSR, and CD lines (pins 2, 6, and 8, respectively) are always high (approximately +5
DC volts when compared to pin 7), and the CTS line (pin 5) is low (approximately -15 volts to pin 7).
When printing is attempted, the KATC-C1 will raise the CTS line and look for high DTR and RTS
before it starts transmitting data. The KATC-C1 will check both of these lines before it sends each
byte of data. If the KATC-C1 does not detect BOTH of these signals high within approximately one
second, the transmission attempt is aborted. At the end of a successful transmission (or an aborted
attempt) the signal lines will be returned to their normal states (TD, DSR, and CD high; CTS low).
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