HMR2300-D20-232 Honeywell, HMR2300-D20-232 Datasheet - Page 6

• Manufacturer Part Number: HMR2300-D20-232
• Manufacturer: Honeywell

Specifications of HMR2300-D20-232

• Lead Free Status / Rohs Status: Compliant

HMR2300
RS-485 BALANCED I/O INTERCONNECTS – Figure 7
DATA COMMUNICATIONS
The RS-232 signals are single-ended undirectional levels that are sent received simultaneously (full duplex). One
signal is from the host personal computer (PC) transmit (TD) to the HMR2300 receive (RD) data line, and the other is
from the HMR2300 TD to the PC RD data line. When a logic one is sent, either the TD or RD line will drive to about
+6 Volts referenced to ground. For a logic zero, the TD or RD line will drive to about –6 Volts below ground. Since the
signals are transmitted and dependent on an absolute voltage level, this limits the distance of transmission due to
line noise and signal to about 60 feet.
When using RS-485, the signals are balanced differential transmissions sharing the same lines (half-duplex). This
means that logic one the transmitting end will drive the B line at least 1.5 Volts higher than the A line. For a logic
zero, the transmitting end will drive the B line at least 1.5 Volts lower than the A line. Since the signals are
transmitted as difference voltage level, these signals can withstand high noise environments or over very long
distances where line loss may be a problem; up to 4000 feet. Note that long RS-485 lines should be terminated at
both ends with 120-ohm resistors.
Another precaution on RS-485 operation is that when the HMR2300 is in a continuous output mode of operation, the
host PC may have to send repeated escape and carriage return bytes to stop the stream of output data. If the host
can detect a recieved carriage return byte (0D hex), and immediately send the escape-carriage return bytes; then a
systematic stop of continuous output is likely. If manually sent, beware that the half-duplex nature of the interface
corrupt the HMR2300 outbound data while attempting to get the stop command interleaved between the data.
As noted by the Digital I/O timing specification and Figure 3, the HMR2300 has a delayed response feature based on
the programmed device ID in response to global address commands (*99….<cr>). Each HMR2300 will take its turn
responding so that units do not transmit simultaneously (no contension). These delays also apply to the RS-232
interface versions of the HMR2300.
Solid State Electronics Center • www.magneticsensors.com • [phone] • Page 6
D
D
HOST PC
HOST PC
Z = 120 ohms
R
R
A -
A -
Z
B+
B+
RD(A)
RD(A)
RD(A)
TD(B)
TD(B)
TD(B)
HMR2300
HMR2300
HMR2300
ID = 01
ID = 01
ID = 01
R
R
R
D
D
D
RD(A)
RD(A)
RD(A)
TD(B)
TD(B)
TD(B)
HMR2300
HMR2300
HMR2300
ID = 02
ID = 02
ID = 02
R
R
R
D
D
D
SENSOR PRODUCTS
Z
Z