Omega Vehicle Security PTC900 - Manual (Page 23)

23
Abbreviated Transmission (
=
)
✰ These characters only appear in the last line of a block print.
The abbreviated response suppresses the address and register mnemonics,
leaving only the numeric part of the response.
Note: Transmissions are formatted to match the way the parameter is displayed.
This includes setpoints.
Example: SP1 assigned to RTC. RTC format = 12:00 P.
SP1 printout = 12:00 P.
Meter Response Examples:
1. Address = 17, full field response, Cycle Counter = 875
17 CNT 875 <CR><LF>
2. Address = 0, full field response, Setpoint 2 = 250.5
SP2 250.5<CR><LF>
3. Address = 0, abbreviated response, Setpoint 2 = 250, last line of block print
250<CR><LF><SP><CR><LF>
Auto/Manual Mode Register (MMR) ID: U
This register sets the controlling mode for the outputs. In Auto Mode (0) the
meter controls the setpoint output. In Manual Mode (1) the outputs are defined
by the registers SOR. When transferring from auto mode to manual mode, the
meter holds the last output value (until the register is changed by a write). Each
output may be independently changed to auto or manual. In a write command
string (VU), any character besides 0 or 1 in a field will not change the
corresponding output mode.
U abcd
d = SP4
c = SP3
b = SP2
a = SP1
Example: VU0011 places SP3 and SP4 in manual.
Setpoint Output Register (SOR) ID: X
This register is used to view or change the states of the setpoint outputs.
Reading from this register (TX) will show the present state of all the setpoint
outputs. A “0” in the setpoint location means the output is inactive and a “1”
means the output is active. The output logic parameter in Module 6 will affect
the active logic state.
X abcd
d = SP4
c = SP3
b = SP2
a = SP1
In Automatic Mode, the meter controls the setpoint output state. In Manual
Mode, writing to this register (VX) will change the output state. Sending any
character besides 0 or 1 in a field or if the corresponding output was not first in
manual mode, the corresponding output value will not change.
Example: VX10* will result in output 1 active and output 2 inactive.
BYTE DESCRIPTION
1-12 12 byte data field, 6 bytes for number, up to 3 bytes for decimal points.
13 <CR> (Carriage return)
14 <LF> (Line feed)
15 <SP> (Space) ✰
16 <CR> (Carriage return) ✰
17 <LF> (Line feed) ✰
50-100 msec. for *
2-50 msec. for $ Print P
50-100 msec. for *
2-50 msec. for $ Transmit T
100-200 msec. Write V
2-50 msec. Reset R
PROCESS TIME (t
2
) COMMENT COMMAND
COMMAND RESPONSE TIME
The meter can only receive data or transmit data at any one time (half-duplex
operation). During RS232 transmissions, 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.
Refer to the Timing Diagrams below. 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 (*, $) is received by
the meter. The time duration of t
1
is dependent on the number of characters and
baud rate of the channel.
t
1
= (10 times the # of characters) / baud rate
At the start of time interval t
2
, the meter starts the interpretation of the
command and when complete, performs the command function. This time
interval t
2
varies. If no response from the meter is expected, the meter is ready
to accept another command.
If the meter is to reply with data, the time interval t
2
is controlled by the use
of the command terminating character. The '*' terminating character results in a
response time window of 50 msec. minimum and 100 msec. maximum. This
allows sufficient time for the release of the sending driver on the RS485 bus.
Terminating the command line with '$' 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. At the end of t
3
, the meter is
ready to receive the next command.
t
3
= (10 times the # of characters) / baud rate
NO REPLY FROM METER
RESPONSE FROM METER
Timing Diagrams
SERIAL TIMING