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TTI-7 Iss.02 – 06/11
REMOTE CONTROL INTERFACES
INTRODUCTION
Version History
Ver 7.1 (ECN 253) DATAlogger:CLEAr command corrected to DATAlogger:CLEar. Both versions will be accepted
to maintain backward compatability.
Ver 7.0 (ECN 239) added Type ‘L’, ‘U’ & AuPt thermocouples, SPRT probes and Pt25 probes. The obsolete IEC751
and US/JIS standards for resistance to temperature conversion were deleted.
Commands for the Rolling Mean & Standard Deviation were added, together with the MEMory:COEFficient?
command.
Ver 6.2 (ECN 149) added the facility to send probe voltage and resistance values over
the bus, using the FETCh[:<function>]? command.
Ver 6.0 (ECN 112) incorporated the Scanner facility commands.
Ver 5.0 (ECN 76) incorporated automatic detection of model ID links.
RS-232 SERIAL INTERFACE
Connection
This conforms to specification ANSI/EIA/TIA-232-E-1991 "Interface Between Terminal Equipment and Data Circuit-
Terminating Equipment Employing Serial Binary Data Interchange." A list of pin assignments is given in Appendix II.
Signal levels:
MARK (logical "1"): -3V to -15V
SPACE (logical "0"): +3V to +15V
Data is transferred using the TXD and RXD lines.
Hardware handshaking for each character transfer uses the RTS and CTS lines.
RTS is an output from the instrument which indicates its receiver status. When asserted (low) it indicates that it is
ready to receive another character. When negated (high) the instrument receiver buffer is full and cannot receive
another character until the buffer is processed (if the PC sends one it may be lost). As soon as space becomes
available in the receiver buffer, RTS is re-asserted to allow the PC to send the next character.
When the instrument detects receipt of a line terminator character, RTS is negated whilst the command line buffer is
read and validated. This is to prevent the PC sending further characters whilst a command is being validated.
Following validation, RTS is re-asserted to permit the next command to be transmitted by the PC.
CTS is an input to the instrument and controls the transmission of characters. If the PC asserts CTS (low) then the
instrument will transmit the next character from the output buffer (if one is waiting). If the PC negates CTS (high)
then the instrument will not transmit the character, but will wait until CTS is re-asserted. TXD will remain in the
mark (low) condition whilst CTS is negated. Note that changing CTS during transmission of a character will not
disrupt the transmission of that character.
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