DayTronic 3500 Series, Instruction Manual

Page: 101 / 122

B.1
I
NTRODUCTION
: RS-232
AND
RS-485 M
ODES
WHEN A 3500 INSTRUMENT'S INTERFACE PORT IS SET TO RS-232 MODE, every
valid INTERROGATION command received at that port will elicit an appropriate
RESPONSE, as will the special transmission-initiating commands
CHANNEL (CHN)
and DUMP (DMP) , described in Section 5.a. Suppose, for example, that an interro-
gation of HIL [CMT] is received, where [CMT] is the INPUT (or "COMMAND") TERMI-
NATOR which the instrument has been instructed to recognize (see Section 3.a.3).
An answer of
h [EOT] will be returned, where "h" is the current HIGH LIMIT setting
and [EOT] is the OUTPUT (or "END-OF-TRANSMISSION") TERMINATOR which the
instrument has been instructed to issue at the end of every transmission from its
RS-232/485 Port (again, see Section 3.a.3).
Note that NO response is given to a SETUP COMMAND such as HIL = h [CMT] or to
an IMPERATIVE COMMAND such as RLS [CMT] when the interface is in the RS-232
mode.
HOWEVER, WHEN THE INTERFACE PORT IS SET TO RS-485 MODE, EVERY
MNEMONIC COMMAND—OF ANY TYPE, "VALID" OR "INVALID"—will elicit an appro-
priate response, as explained below.
B.2
T
HE
OPEN (OPN) C
OMMAND
As mentioned in Section 5.a.3, OPEN (OPN) is the only computer-issued command
directed to a multinode network as a whole (each node having been set to RS-485
communications). The "opened" node (only) will return to the computer an "acknowl-
edgement" of
ACK [EOT]
ALL OTHER MNEMONIC COMMANDS ISSUED TO THE NETWORK WILL BE DIRECT-
ED EXCLUSIVELY TO THE CURRENTLY "OPEN" NODE.
B.3
R
ESPONSE TO
“I
NVALID
” C
OMMANDS
WHEN IN RS-485 MODE, RECEIPT BY A 3500 INSTRUMENT OF AN "INVALID" COM-
MAND OF ANY KIND WILL PRODUCE A RESPONSE OF "NOT ACKNOWLEDGED":
NAK [EOT]
An "invalid" command may be one which does not appear on the list below, or which
contains an unacceptable range or other element. An invalid command will elicit NO
RESPONSE when the interface is set to RS-232 mode.
All other commands fall into four basic categories:
B.1
C
OMMAND AND
R
ESPONSE
S
YNTAX
B
B.1 I
NTRODUCTION
B.2 T
HE
OPEN C
OMMAND
B.3 R
ESPONSE TO
“I
NVALID
” C
OMMANDS
Appendix B
Command and Response Syntax