RECEIVING DATA FROM THE IMP
Data is transmitted from the indicator whenever a “T” or “P” command is
received via serial communications or a remote input, E1-CON or optional
E2-CON pin is programmed for print request, is activated. If the abbreviated
transmission was programmed, just data will be transmitted, with no built-in
delay. If full transmission is programmed, then there is a 400 msec min to 800
msec max delay built into the string. A data string transmission is shown below.
The first two 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 three
characters are the abbreviation for the value (mnemonics) which is then followed
by a blank. The actual data is transmitted next. The field is right justified with
leading zeros. Negative numbers are indicated by a minus sign fixed next 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 above character string.
(These characters could be and are used for control or signaling purposes.)
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 unit.
For a “T” command or after each “line of a block” transmission, no additional
characters 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).
If the transmitted data is overrunning the peripheral’s buffer, the receive
channel to the indicator may be used for handshaking purposes. As a
consequence of this, even if the indicator is to transmit only (ex. to a printer),
current must be flowing in the receive channel to allow transmission.
Examples of transmissions are as follows:
2 INP -125.75 < CR> < LF> full transmission
-125.75 < CR> < LF> abbreviated transmission
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