Laurel Electronics Custom ASCII Protocol For Laureate Series 2 Digital Panel Meters, Counters, Timers & L-Series Transmitters - Manual (Page 19)

19
Baud
Rate
Time
1 Item
Min
Gate
Time
2 Items
Min
Gate
Time
3 Items
Min
Gate
Time
4 Items
Min
Gate
300
600
1200
2400
4800
9600
19200
0.37s
0.18s
0.09s
0.05s
0.02s
0.01s
0.01s 0.34s
0.15s
0.06s
0.02s
0.01s
0.01s
0.01s 0.70s
0.35s
0.18s
0.09s
0.04s
0.02s
0.01s 0.67s
0.32s
0.15s
0.06s
0.01s
0.01s
0.01s 10.03s
0.52s
0.26s
0.13s
0.07s
0.03s
0.02s
1.00s
0.49s
0.23s
0.10s
0.04s
0.01s
0.01s 1.37s
0.68s
0.34s
0.17s
0.09s
0.04s
0.01s 1.34s
0.65s
0.31s
0.14s
0.06s
0.01s
0.01s
The data transmission rate may be reduced by sending data every other reading, every fourth
reading, or less. This selection is made in “Ser 1”. A computer, if busy with other tasks, may be
unable to keep up with the faster data rates of the meter, so a handshake function is available
that provides the computer with control over the meters’ data transmissions.
8.3 RTS CONTROL
RTS control does not apply to transmitter, where the RTS line is always held high, nor to
RS485. DPMs and counter / timers have two RS232 RTS modes: unlatched and latched. These
modes are selected in “Ser3”.
In the unlatched mode, the measurement transmission is enabled by a high RTS level and is
disabled by a low RTS level. When disabled, any character being sent is completed. When
enabled, any characters remaining in the data format are transmitted before the next measu-
rement transmission. The computer, when its receive buffer is nearly full, takes the RTS line
low to halt data transmission. When its receive buffer has emptied, it takes the RTS line high to
enable more data transmissions. Some measurements could be missed in the process. In the
latched mode, the RTS input is polled every 3.3 ms. When a high level is detected, RTS is
latched true, even though the RTS line goes low immediately. At the end of each calculation, the
latched RTS value is checked. If it is true, a complete measurement transmission (from 1 to 4
values) is made without interruption, regardless of the state of the RTS line during that time. At
the end of the complete transmission, the latched RTS value is reset false, even though the RTS
line may be high at that instant. The RTS latch does not go true again until the RTS line is first
returned to a low level after the completion of the transmission and then is taken high again.
Latched control provides “print command” operation by sending a transmission for each RTS
pulse. If a second pulse occurs during the transmission, it is not recognized.
8.3 XON / XOFF CONTROL
Applicable to RS232, not RS485. A measurement transmission is enabled by the receipt of an
ASCII XON character. It is disabled by the receipt of an ASCII XOFF character.