SmarTek Systems SAS-1 Detailed Communication Formats User Manual
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SmarTek Systems (www.smarteksys.com)
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Command to SAS-1: Start Dual Zone Relay Signals Reporting
Comm_Mode ia a byte (1-Polled, 2-Periodic) and is offset by +32 (20 Hex).
SAS-1 Response:
Chr(2)SASxxxx<20 bytes>Chr(3)
where SASxxxx is the sensor identification number (i.e. SAS0000, SAS0001, SAS0002, etc.),
Chr (2) and Chr(3) are the start of message and end of message characters. The SAS-1 formats
the vehicle presence relays in a multi-time point, bit serial format. The 20 byte message packet
represents 10 time points with an update time of 8 milli-seconds (one message covers 80 milli-
seconds). The vehicle presence relays for five (5) zones are represented by the first 5 bits of
each byte. Each time point is a pair of bytes with the first byte representing the “upstream
relays” for each of up to 5 lanes and the second byte representing the “downstream relays” for
each of up to 5 lanes. Note that each byte is offset by 32 (20 Hex) to shift the byte data away
from the ASCII control codes. Hence, 32 (20 Hex) must be subtracted from each byte before
interpreting each bit state. The “Loop” spacing for the “dual loop speed trap” emulation is
specified by D_MODE (See the Get Parameter Command). If D_MODE is not set to a value
between 96 and 110, the emulated “Dual Loop” spacing is assumed to be 18 feet. The above
message will be output periodically (every 80 milli-sec) or when polled by a controller using the
following command:
Command to SAS-1: STOP
SAS-1 Response:
SAS-1 Stops current communications.
Command to SAS-1: Get SAS-1 Parameters
SAS-1 Response: