Laurel Electronics LAUREATE SERIES Serial Comunications - Manual (Page 12)

Counter only
The transmission rate of measurement data can be selected in “Ser 1". Data transmission is
initiated at the end of the calculation time following the gate time. Data is completely transmitted
for one measurement before the calculation of the next measurement is started. Therefore, the
reading rate is influenced by the baud rate, the number of items transmitted and gate time. If the
selected gate time is less than that shown in the table below, it is not the determining factor of the
reading rate. If it is greater, then it is the determining factor. Time intervals (reciprocal of rate)
between transmissions at the reading rate are:
TIME MIN TIME MIN TIME MIN TIME MIN
BAUD 1 ITEM GATE 2 ITEMS GATE 3 ITEMS GATE 4 ITEMS GATE
300 .37s .34s .70s .67s 1.03s 1.00s 1.37s 1.34s
600 .18s .15s .35s .32s .52s .49s .68s .65s
1200 .09s .06s .18s .15s .26s .23s .34s .31s
2400 .05s .02s .09s .06s .13s .10s .17s .14s
4800 .02s .01s .04s .01s .07s .04s .09s .06s
9600 .01s .01s .02s .01s .03s .01s .04s .01s
19200 .01s .01s .01s .01s .02s .01s .02s .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. Both hardware (RTS) and software (XON/XOFF) handshaking are available
for the RS232 option but neither is available for the RS485 option.
RTS
he meters have 2 modes for RTS control, unlatched and latched. In the unlatched mode, the
measurement transmission is enabled by a high RTS level, and disabled by a low RTS level. When
disabled, any character being sent is completed and when enabled any characters remaining in
the data format are transmitted before the next measurement 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. The latched and unlatched mode are selected in
"config" "digit 2" in the DPM and in the Counter and Scale meter by “Ser 3” .
With latched control, the RTS input is polled every 3.3mS and 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 and if it is true, a complete measurement transmission (from one to
four values) is made without interruption regardless of the state of the RTS line during that time.
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