Receiving Data from the IMY, Current Loop Installation

RECEIVING DATA FROM THE IMY

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

800msec max delay built-in to 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.

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.

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Examples of transmissions are as follows:	full transmission
2 INP -125.7F < CR> < LF >	full transmission
-125.7 < CR> < LF >	abbreviated transmission

CURRENT LOOP INSTALLATION

WIRING CONNECTIONS

When wiring 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 terminal descriptions below or those located on the label. It is recommended that shielded (screened) cable be used for serial communications. This unit meets the EMC specifications using Alpha #2404 cable or equivalent. There are higher grades of shielded cable, such as four conductor twisted pair, that offer an even higher degree of noise immunity. Install each wire in its proper location on the terminal block. When all connections are made, replace the terminal block into its proper location.

SERIAL TERMINAL DESCRIPTIONS

8. PRINT REQ. - The Print Request terminal is pulled low to activate the unit to transmit data according to the print function selected in Program Module #7 (Reference Programming Module #7 for more details). In order for a print request 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. Current flows into this pin.

10. SI+ (Serial In+) -

11. SI- (Serial In-) -

The unit receives commands on the SI terminals. They are connected in series with the 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 connected in 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) in order for the unit to respond to a Print Request terminal activation.