CH1787(1998) View Datasheet(PDF) - Cermetek Microelectronics
Part Name
Description
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CH1787 Datasheet PDF : 13 Pages
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PIN NAME
I/O
FUNCTION
20
GND
I
GROUND.
21
____
DCD
22
__
HS
23
____
ORG
O
DATA CARRIER DETECT output. LOW indicates a data carrier from a remote modem is detected.
DCD follows carrier is the default.
O
SPEED INDICATION. High speed select output. A LOW on this pin indicates the modem is
operating at 2400bps.
Originate input (active LOW) places to modem off hook in the originating mode without dialing. Used
I
to make a connection on dedicated leased lines between two points. The remote modem must be in
answering mode.
24
NC
-
No Connection
25
NC
-
No connection.
26
NC
27
SPK
-
No connection.
O
SPEAKER - Audio Output. See Figure 5.
28
___
TST
I
Test pin input used in conjunction with ORA to steer the dialing between a user stored number and a
pre-stored Cermetek test number. See ORA description.
29
____
CON
30
____
HNG
31
____
RXD
32
VCC
33
GND
O
Connect output indicates a valid 2400bps connection. Can be used in place of DCD and HS to start
the communications. Can be used to indicate the start of an exchange of data.
I
The hang-up input pin (active LOW), forces the modem to disconnect. The HNG pin is only functional
when DCD is active (low).
O
RECEIVE DATA. Serial receive data output. Received MARKING or a binary 1 condition is indicated
by a HIGH.
I
5 Volts + 5% Note: Noise should be less than 50MV.
I
GROUND.
34
____
AAR
AAR pin is an input (active LOW). When asserted low then high, CH1787 will auto answer during a
I
Ring cycle. AAR can be tied low primarily to enable Auto Answer on the first RING. AAR will not
override an AT auto answer condition e.g., S0 > 1.
Spare pins are available for custom functions. Contact Cermetek with your requirements.
Cermetek Microelectronics, Inc.
Document No. 603-0182 Rev. D (11/98) 5
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