ch1786nh ETC-unknow, ch1786nh Datasheet - Page 4

• Manufacturer Part Number: ch1786nh
• Description: Ch1786 Family Ultra Small 2400bps Modems
• Manufacturer: ETC-unknow

Cermetek Microelectronics, Inc.
normal operation the CH1786 decodes analog signals
from the telephone line that are in the millivolt range.
Steps must be taken by the user to guarantee that
power supply noise on all supply lines, including
ground, does not exceed 50 mV peak to peak. Any
frequency between 20 kHz and 150 kHz must be less
than 500 micro volts peak.
dedicated power and ground planes.
provide such operating conditions could cause the
CH1786 to malfunction or to function erratically.
The CH1786 requires a single +5V ±5% supply. It is
recommended that by-pass capacitors be placed on
the power supply as close to the modem’s supply
input as practical.
Tantalum capacitor in parallel with a 0.01 µF ceramic
capacitor be used.
Voice/DTMF Tone Injection Port.
provides two pins to allow the user to share the
telephone line interface associated with the modem
for voice and DTMF applications. Figure 4 contains a
schematic indicating one possible configuration for
voice/ tone utilization.
Typically, voice communication would precede data
communications.
commands should be used to configure the CH1786
(Refer to Figure 4):
Figure 4. Voice/Tone Injection.
Enter: ATS0=<CR>
Result: OK
2003 Cermetek Microelectronics, Inc.
WARNING: The CH1786 has been FCC Part 68
approved as a data modem only. Utilization of
the Voice/DTMF Tone Port requires further
registration. FCC will require that the system,
including the CH1786 and the handset or DTMF
transceiver, adhere to Part 68 rules. Voice/Tone
Injection is not active on CH1786NH.
For this case, the following
It’s recommended a 10 µF
Disables auto-answer
If necessary, use
The CH1786
Failure to
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Enter: ATS7=255<CR>
Result: OK
Enter: ATS10=255<CR> Disables lost-carrier time
Result: OK
The following command sequences illustrate
implementation of common Voice/Tone Port
applications.
1. To answer a voice call.
2. To switch to data mode.
3. To disconnect (hang-up) a voice call or a data
4. To place a call to 1234567 using the CH1786’s
MODEM CONTROL
The CH1786 modem may be controlled by sending
serial ASCII command sequences. The commands
are sent to the modem serially on the TXD pin. After
execution of a received command, the modem
returns a serial status message that can be read on
pin RXD.
completion status. Refer to Table 3 for a complete
list of status messages.
INITIALIZING THE MODEM
Before commands may be sent to the CH1786, the
CH1786 must be initialized. Initialization is a two step
activity consisting of:
1. Hard Reset. This is accomplished by applying a
2. Initial modem training.
These activities are briefly described below.
hardware reset pulse to pin RST or by switching
the power off and then back on.
trained to the host ’s speed (2400,1200,300bps)
and parity (odd, even, mark, space or none).
(a) Enter: ATH1<CR>
(b) Drive V.INJ. HIGH to activate relay.
(c) Begin voice conversation.
(a) Drive V.INJ. LOW
(b) At the originate modem:
call.
(a) Enter: ATH<CR>
DTMF tone generator.
(a) Enter: ATDT1234567;C0<CR>
(b) Drive V.INJ. HIGH
Result: OK
Result: OK
Result: OK
Result: OK
Enter: ATX1<CR>
CH1786 Family of Ultra Small 2400bps Modems
This message indicates command
Document No. 607-0004 Revision L1 (06/03)
Disables data-carrier time
out
out
The CH1786 must be