Red Lion PAXCDC1,2 (RS232/RS485) - Manual (Page 5)

5
(CSR) Control Status Register
The Control Status Register is used to both directly control the meter’s
outputs (setpoints and analog output), and interrogate the state of the setpoint
outputs. The register is bit mapped with each bit position within the register
assigned to a particular control function. The control function are invoked by
writing to each bit position. The bit position definitions are:
Although the register is bit mapped starting with bit 7, HEX < > characters
are sent in the command string. Bits 7 and 5 always stay a zero, even if a “1” is
sent. This allows ASCII characters to be used with terminals that may not have
extended character capabilities.
Writing a “1” to bit 4 of CSR selects manual mode. In this mode, the setpoint
outputs are defined by the values written to the bits b0, b1, b2, b3; and the
analog output is defined by the value written to the AOR. Internal control of
these outputs is then overridden.
In automatic mode, the setpoint outputs can only be reset off. Writing to the
setpoint output bits of the CSR has the same effect as a Reset command (R).
The contents of the CSR may be read to interrogate the state of the setpoint
outputs and to check the status of the temperature sensor (PAXT only).
Examples:
1. Set manual mode, turn all setpoints off:
V is command write, J is CSR and * is terminator.
2. Turn SP1, SP3 outputs on and SP2, SP4 outputs off:
3. Select Automatic mode:
Note: Avoid writing values <0A> (LF), <0D> (CR), <24> ($) and <2E> (*)
to the CSR. These values are interpreted by the meter as end of command
control codes and will prematurely end the write operation.
(AOR) Analog Output Register
The Analog Output Register controls the analog output of the meter. The
manual mode must first be engaged by setting bit 4 of the Control Status
Register. The range of values of this register is 0 to 4095, which corresponds to
0 mA, 0 V and 20 mA, 10 V; respectively. The table lists correspondence of the
output signal with the register value.
*Due to the absolute accuracy
rating and resolution of the output
card, the actual output signal may
differ 0.15% FS from the table
values. The output signal
corresponds to the range selected
(20 mA or 10 V).
Writing to this register while the meter is in the manual mode causes the
output signal to update immediately. While in the automatic mode, this register
may be written to, but the output will not update until the meter is placed in
manual mode.
Examples:
1. Set output to full scale:
VI4095*
2. Set output to zero scale:
VI0*
bit 0: Setpoint 1 Output Status
0 = output off
1 = output on
bit 1: Setpoint 2 Output Status
0 = output off
1 = output on
bit 2: Setpoint 3 Output Status
0 = output off
1 = output on
bit 3: Setpoint 4 Output Status
0 = output off
1 = output on
bit 4: Manual Mode
0 = automatic mode
1 = manual mode
bit 5: Always stays 0, even if 1 is sent.
bit 6: Sensor Status (PAXT only)
0 = sensor normal
1 = sensor fail
bit 7: Always stays 0, even if 1 is sent.
SERIAL COMMANDS FOR PAX SOFTWARE
7 6 5 4 3 2 1 0:bit location
VJ<30>* or VJ0* ASCII 0 = 0 0 1 1 0 0 0 0 or <30>
VJ<35>* or VJ5* or <35> 1 0 1 0 1 1 0 0 ASCII 5 =
0:bit location 1 2 3 4 5 6 7
VJ<40>* or VJ@* or <40> 0 0 0 0 0 0 1 0 ASCII @ =
0:bit location 1 2 3 4 5 6 7
Command Response Time
The meter can only receive data or transmit data at any one time (half-duplex
operation). The meter ignores commands while transmitting data, but instead
uses RXD as a busy signal. When sending commands and data to the meter, a
delay must be imposed before sending another command. This allows enough
time for the meter to process the command and prepare for the next command.
At the start of the time interval t
1
, the computer program prints or writes the
string to the com port, thus initiating a transmission. During t
1
, the command
characters are under transmission and at the end of this period, the command
terminating character (*) is received by the meter. The time duration of t
1
is
dependent on the number of characters and baud rate of the channel.
t
1
= (10 * # of characters) / baud rate
At the start of time interval t
2
, the meter starts the interpretation of the
command and when complete, performs the command function. This time
interval t
2
varies from 2 msec to 50 msec. If no response from the meter is
expected, the meter is ready to accept another command.
If the meter is to reply with data, the time interval t
2
is controlled by the use
of the command terminating character. The standard command line terminating
character is ‘*’. This terminating character results in a response time window of
50 msec minimum and 100 msec maximum. This allows sufficient time for the
release of the sending driver on the RS485 bus. Terminating the command line
with ‘$’ results in a response time window (t
2
) of 2 msec minimum and 50 msec
maximum. The faster response time of this terminating character requires that
sending drivers release within 2 msec after the terminating character is received.
At the beginning of time interval t
3
, the meter responds with the first
character of the reply. As with t
1
, the time duration of t
3
is dependent on the
number of characters and baud rate of the channel. t
3
= (10 * # of characters) /
baud rate. At the end of t
3
, the meter is ready to receive the next command.
The maximum serial throughput of the meter is limited to the sum of the
times t
1
, t
2
and t
3
.
Ready Ready
1
t t
2
Ready t
1
t
2
Ready t
3
Command
String
Transmission
Meter
Response
Time
Command
Terminator
Received
First
Character
of Reply
Reply
Transmission
NO REPLY FROM METER
RESPONSE FROM METER
Time
Timing Diagram Figure
Register Value
Output Signal*
I (mA) V (V)
0.000 0.000 0
1 0.005 0.0025
5.000 10.000 2047
4094 19.995 9.9975
10.000 20.000 4095