Cooper Instruments & Systems DFI 200 Hand Held Indicator - Manual (Page 17)

CF 112 17 Version 3.1-0
(set RS232/485 interface mode) Select or . Allows user to select the RS232/485
interface operation as follows:-
• - Sends image data from the display without conversion to ASCII. This mode is intended for use
only when the DFI 200 is used to transmit data to a compatible display.
•
- Sends ASCII form of display data every time display is updated.
• - Controlled by computer or PLC as host. Host sends command via RS232 and the instrument
responds as requested in ASCII form. See “Poll commands” section which follows.
•
- This is a special communications mode used with Windows compatible optional PC download
software. Refer to the user manual supplied with this optional software.
(set unit address for polled ( ) mode (0 to 31)).
Allows an individual address to be assigned to a number of DFI 200 instruments. The instrument will respond with
its address proceeding the display reading. The unit address ranges from 0 to 31 (DEC) but is offset by 32 (DEC) to
avoid clashing with ASCII special function characters (such as <STX> and <CR>). Therefore 32 (DEC) or 20 (HEX)
or SPACE (ASCII) is address 0 whilst 42 (DEC) or 2A (HEX) or _ (ASCII) is address 10. If the host computer or
PLC etc. uses address 0 when polling then the DFI 200 connected to the host will always respond no matter what
the
function setting. If the host uses any other address then only instruments with the same address will
respond to a polling command.
Poll commands - Host Controlled Transmit Mode:
This mode requires a host computer or PLC to poll the instrument to obtain display or other information or reset
various setpoint parameters. Communications software often known as a “terminal” program is required when using
mode. When polling the DFI 200 it is essential that the command characters are sent with less than a
10mS delay between them. This means that each command line must be sent as a whole string e.g.
<STX>PA<CR> is sent as one string rather than <STX> on one line followed by P etc. If testing using a terminal
program this is normally achieved by allocating a command string to a function key. Whenever the function key is
operated the whole string is sent. The format used is ASCII (8 data bits + 1 stop bit) so, for instance, if address 1 is
used then the string <STX>PA<CR> would typically be put into the terminal program as: ^BP!^M
Where:
^B is the ASCII character for STX
P is the command line to transmit the primary display value
! is the ASCII character for address 1 (33 Dec of 21 Hex)
^M is the ASCII character for CR