ECM BB100, Инструкция по эксплуатации, Страница: 20 / 37

RS-232 Output:
•
DB9M connector on BB100
•
Pin 2 Tx (from BB100), Pin 3 Rx (to BB100), Pin 5 Ground
•
Use “straight-through” cable to PC
Serial Port Programming Interface Description
Background
The BB100 may be operated under remote control using a standard RS-232 serial port. The
interface allows easy integration of the BB100 into virtually all data acquisition systems.
Any operation which is possible with the front panel keys may be performed remotely using
serial port commands. The flow calibration curve may also be uploaded and downloaded
using the interface. For examples of remote control operation, try using the BBREMOTE
(MS-DOS PC) software included with the BB100.
The BB100 may be operated both under remote control and “local” control at the same time.
Setup parameters such as the operating mode may be changed either on the meter or with the
serial port interface. The most recent command received by the meter will set the value of
the parameter.
Real-time flow data may be uploaded using a poll command. Values for all four of the
possible operating modes (LPM, CFM, Liters Total, or Ft
3
Total) are uploaded when a real-
time poll command is executed. This allows the operating mode of the meter to be changed
on the front panel during remote operation without affecting the flow values received by the
data acquisition system.
Serial Port Commands
The external computer may issue commands to the BB100 only when it is displaying a flow
value. The BB100 will not react to serial port commands during initialization or when in the
setup menu. The serial port parameters are 4800 baud, no parity, 8 data bits, 1 stop bit.
Many of the commands are acknowledged by the BB100 with a two byte code indicating the
success or failure of the command. The two byte positive acknowledgment is <D0> <D0>.
The negative (fail) acknowledgment is <D1> <D1>. Some commands are not acknowledged
since performance of the requested function may be used as an acknowledgment. For
example, the poll command for real-time data is “acknowledged” by the presence or absence
of the real-time data.
The BB100 stores setup and calibration data either as one byte “selections” or as four byte
floating point “constants”. The four byte floating point constants have the low byte (the least
significant byte of the fraction part) first. This is consistent with an Intel PC format. An
example of a “selection” is the choice of the operating mode (LPM, CFM, Liters Total, or Ft
3
Total). The “constants” are the meter calibration curve values.
There are five serial port command formats: “Control”, “Download Selection”, “Download
Value”, “Upload Selection”, and “Upload Value”.
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