Cermetek Microelectronics, Inc.
CH1788 Surface Mount PLCC 2400bps Modem
2006 Cermetek Microelectronics, Inc.
Page 10
Document No. 607-0018 Revision A6 (01/06)
Escape Sequence.
The escape sequence consists
of a “guard time” of one second (a period where no
characters are sent to the modem), followed by 3
escape characters (typically
+++
), followed by
another guard time of one second. The escape
character code is set in register S2. By default, the
escape character is set as “+.” There is no required
delay between characters. When the escape
sequence has successfully been sent, the escape
characters will not be transmitted to the remote
modem.
The CH1788 will stay Off-Hook with its carrier on after
the escape sequence is received. It will return an OK
status message on RXD when it is ready to accept
commands. The CH1788 may be put into data mode
again by issuing the command
ATO
.
AT COMMAND APPLICATIONS
Dialing a phone number.
The Dial command takes
the form
Dn
, where
n
is a string of characters. In the
simplest form,
n
will be the digits of the phone
number to be dialed.
Example: Dial number.
Enter:
ATD1234567<CR>
Result:
OK
In the above example, the CH1788 dials the
telephone number
1234567
, conducts handshaking
negotiations then waits for a carrier from the distant
modem. If a carrier is not detected within the time
period specified by register S7, the CH1788 will
automatically release the PSTN line and send the
appropriate result code to the host. If a carrier is
detected, the CH1788 will send the CONNECT result
code and will permit communication with the distant
modem. Note, the CH1788 is ready to send and
receive data after the CONNECT result code is sent
or when an active signal is present on DCD. DCD
line must be enabled with the
ATC1
command.
A variety of dial modifiers can be placed in the dialing
string to make it application specific. These include
pause, hook flash, pulse dialing, wait for dial tone,
etc. See the detailed
D
command.
The Dial Command may also be issued without a
telephone number.
ATD
causes the modem to pick
up the telephone line without dialing a number.
Programmable S-Registers.
The CH1788 contains
a variety of registers that store the configuration and
personality parameters for the CH1788. Both default
configuration and user specified configuration
parameters are stored. A summary of the S-
Registers is given in Table 4. A detailed description
of each is available in CH1788 Command and S-
Register Reference Guide. Do not attempt to modify
S-Registers that are not listed in the table.
Table 4. CH1788 S-Register Summary.
Register Function
S0*
Ring to Answer On
S1 Ring
Count
S2
Escape Code Character
S3 Carriage
Return Character
S4
Line Feed Character
S5
Back Space Character
S6
Wait for Dial tone
S7
Wait for Data Carrier
S8
Pause Time for Comma
S9
Carrier Detect Response Time
S10
Lost Carrier to Hang-up Delay
S11 DTMF
Tone
On/Off
S13
DTMF Data/ Transmit Attenuation
S17
Ring Minimum Frequency
S18
Ring Maximum Frequency
S23
Call Progress Functions
S30
Data Modulation Selection
S31
Data Modulation Status
S51
Ring/ Cadence A minimum On-Time
S52
Ring/ Cadence A maximum On-Time
S53
Ring/ Cadence A minimum Off-Time
S54
Ring/ Cadence A maximum Off-Time
S55
Ring/ Cadence B minimum On-Time
S56
Ring/ Cadence B maximum On-Time
S57
Ring/ Cadence B minimum Off-Time
S58
Ring/ Cadence B maximum Off-Time
S65 DTMF
Detection
S66
Wait For Dial Tone Timer
S67
Minimum Duration Of Dial Tone
S68 Test
Timer
S69 Test
Error
Count
S86
Hook Flash On Time
S89 Fast
Connect/Pickup
S95
Caller ID configuration
S110
Line-In-Use/ Parallel Pick-Up
Register
S111
Line-In-Use Setting Time
Automatic Answering.
Register S0 specifies the
number of rings that the CH1788 must detect before it
will answer. S0 may range in value from 0 to 255.
S0 =0 DO NOT ANSWER TELEPHONE
S0 =1 ANSWER ON RING 1
S0 =2 ANSWER ON RING 2
S0 =3 ANSWER ON RING 3
S0 =255 ANSWER ON RING 255
When S0 is set to 0, the modem will not answer.
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
