ELM627
Pin Descriptions
VDD (pin 1)
Otherwise, the output will remain active
continuously until pin 5 returns to a logical low
level. The output duration will always be a
minimum of 10ms, and is 100ms on powerup.
This pin is the positive supply pin, and should
always be the most positive point in the circuit.
Internal circuitry connected to this pin is used to
provide power on reset of the microprocessor, so
an external reset signal is not required. Refer to
the Electrical Characteristics section for further
information.
TxD (pin 5)
This is the monitored signal input, usually
connected directly to the RS232 Transmit Data
line through a suitable current limiting resistor.
This input employs Schmitt trigger logic so that
input waveshaping circuitry is not normally
required.
Q (pin 2)
This signal is driven to a logical high level when a
break signal is detected, and during powerup.
T1 (pin 6) and T0 (pin 7)
Q (pin 3)
These are the threshold setting inputs. Logic
levels on these pins at the rising edge of TxD are
used to determine the required minimum duration
of the break signal, as shown in Table 1 below.
This output signal is normally held at a high level,
and is driven low when a break signal is detected,
as well as immediately after powerup.
P/C (pin 4)
VSS (pin 8)
This is the pulse/continuous control input pin,
used to modify the behavior of the circuit output.
If at a logic high when a break signal is detected,
the output will consist of a single 100ms pulse.
Circuit common is connected to this pin. This is
the most negative point in the circuit.
Threshold Setting
Min Break Signal Baud rate, ‘00’ character sent
(msec)
T1
T0
will trigger at
but not at
L
L
L
H
L
5.0
11
1200
600
300
-
2400
1200
600
H
H
22
H
120
110
Table 1. Threshold Settings
Ordering Information
These integrated circuits are available in either the 300 mil plastic DIP format, or in the 200 mil SOIC surface
mount type of package. To order, add the appropriate suffix to the part number:
300 mil Plastic DIP............................... ELM627P
200 mil SOIC..................................... ELM627SM
All rights reserved. Copyright ©1998 Elm Electronics.
Every effort is made to verify the accuracy of information provided in this document, but no representation or warranty can be
given and no liability assumed by Elm Electronics with respect to the accuracy and/or use of any products or information
described in this document. Elm Electronics will not be responsible for any patent infringements arising from the use of these
products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or
systems. Elm Electronics reserves the right to make changes to the device(s) described in this document in order to improve
reliability, function, or design.
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ELM627DSA
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