RECEIVING DATAFROM THE IMY
Datais transmitted from the indicator whenever a “T” or “P” command is
receivedvia serial communications or a remote input, E1-CON or optional
E2-CONpin is programmed for print request, is activated. If the abbreviated
transmissionwas programmed, just data will be transmitted with no built-in
delay.(If full transmission is programmed, then there is a 400 msec min to
800msec max delay built-in to the string.)
Adata string transmission is shown below.
Thefirsttwo characters transmitted are the unit address number, unless it is
zero,in which case it is left blank. Then two blank spaces are sent. The next
threecharacters are the abbreviation for the value (mnemonics), which is then
followed by a blank. The actual data is transmitted next. The field is right
justifiedwith leading zeros. Negative numbers are indicated by a minus sign
fixednext to the identifier. A carriage return and a line feed are transmitted
next.For various reasons, “extra” characters are added onto the end of the
abovecharacter string. (These characters could be and are used for control or
signalingpurposes.) These characters are:
<CR> sent after single line transmissions from IM unit.
<SP>< CR>< LF> sent after “last line of a block” transmission from IM.
For a “T” command or after each “line of a block” transmission, no
additionalcharacters are sent. If the abbreviated transmission is selected, the
address, mnemonics, and any blank spaces (first eight characters) are not
transmitted(the data strings are left justified in this case).
Ifthe transmitted data is overrunning the peripheral’s buffer, the receive
channel to the indicator may be used for handshaking purposes. As a
consequenceof this, even if the indicator is to transmit only (ex. to a printer),
currentmust be flowing in the receive channel to allow transmission.
Examplesof transmissions are as follows:
2INP -125.7F <CR> < LF > fulltransmission
-125.7 < CR> < LF > abbreviatedtransmission
CURRENT LOOP INSTALLATIONWIRING CONNECTIONS
Whenwiring the 20 mA current loop, remove the bottom terminal block
(TBA),located on the rear of the unit. Refer to the numbers listed with the
terminaldescriptions below or those located on the label. It is recommended
thatshielded (screened) cable be used for serial communications. This unit
meetsthe EMC specifications using Alpha #2404 cable or equivalent. There
arehigher grades of shielded cable, such as four conductor twisted pair, that
offeran even higher degree of noise immunity. Install each wire in its proper
locationon the terminal block. When all connections are made, replace the
terminalblock into its proper location.
SERIAL TERMINAL DESCRIPTIONS
8.PRINT REQ. - The Print Request terminal is pulled low to activate the unit
totransmitdata according to the print function selected in Program Module
#7(Reference Programming Module #7 for more details). In order for a
printrequest function to occur, E1-CON (TBA #4) or E2-CON (TBA #8)
must be programmed for print request. Note: In order to guarantee a
print-out, the programmed E-CON pin must be held low for at least 20
msec.If this time exceeds 800 msec, a second print-out may occur.
9. -20 mA SRC. - 20 mA current source return path for the transmit loop.
Currentflows into this pin.
10.SI+ (Serial In+) -
11.SI- (Serial In-) -
Theunit receives commands on the SI terminals. They are connected in
serieswiththe transmit or output terminals of the device to be connected.
12.SO+/+20 mA SRC. (Serial Out+) - 20 mA current source for the transmit
loop(internally connected).
13.SO- (Serial Out-) -
The unit transmits the requested data on the SO terminals. They are
connectedin series to the receive input of the device to be connected.
Note: The Serial Input terminals must be held in the mark condition (current
flowing)inorder for the unit to respond to a Print Request terminal activation.
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