Welch Allyn TM 262 Auto Tymp - User Manual - Manual (Page 79)

Revised 4/11/08 5-13
RS-232 Interface
RS-232 Interface
Interface configuration
The configuration of the TM 262 RS-232 interface must be set to match the interface configura-
tion of the computer. The TM 262 defaults to 9600 baud, no parity, 8 data bits, 2 stop bits and
no communications flow control. The default settings for the baud rate, parity, number of data
bits and flow control may be modified using the Data Transfer Program Mode explained
earlier in this chapter.
Cable connections
The RS-232 interface provides a serial interface consisting of RxD (Received Data) and TxD
(Transmitted Data) using a standard DB-25 female connector. A straight through cable can be
used to connect to either a 25 pin or 9 pin (using an appropriate adapter) connector on the exter-
nal device.
Communications flow control
Software XON/XOFF flow control is available to allow software commands from the external
computer to start and stop the flow of data from your instrument. No hardware flow control is
provided. Sending XOFF (ASCII control character [DC3]) to the instrument pauses its
transmission.
Sending XON (ASCII control character [DC1]) to your instrument resumes the transmission.
Once XOFF is received by the instrument, XON must be received within six seconds. If not
received within this time, then the message “NO RESPONSE” is displayed for about three
seconds, transmission is aborted, and normal operation resumes.
After an XOFF timeout, the next transmission waits for XON to be received within six seconds
as described above.
These commands are valid only during data transmission and when enabled in the Data
Transfer Program Mode.
TM 262
(25 pin)
TD 2
RD 3
Signal 7
Ground
TM 262
(25 pin)
TD 2
RD 3
Signal 7
Ground
Computer
(25 pin)
2 TD
3 RD
7 Signal Ground
Computer
(25 pin)
2 TD
3 RD
7 Signal Ground