3COM CORPORATION
US ROBOTICS 28,800 EXTERNAL
Modem Type |
Data (synchronous/asynchronous)/Fax |
Maximum Data Rate |
28.8Kbps |
Maximum Fax Rate |
14.4Kbps |
Data Bus |
External |
Fax Class |
Class I & II |
Data Modulation Protocol |
Bell 103A/212A ITU-T V.22, V.22bis, V.23, V.32, V.32bis, V.25 |
Fax Modulation Protocol |
ITU-T V.17, V.21CH2, V.27ter, V.29 |
Error Correction/Compression |
MNP5, V.42, V.42bis |
CONNECTIONS | |||
Purpose |
Location |
Purpose |
Location |
Line out |
CN3 |
DC power |
CN1 |
Line in |
CN4 |
Volume |
R1 |
RS-232/422 |
CN2 |
Power switch |
SW2 |
DTR SIGNAL | |
Setting |
SW1/1 |
í DTR normal |
Off |
DTR forced high |
On |
RESULT CODES | |
Setting |
SW1/2 |
í Verbal result codes enabled |
Off |
Numeric result codes enabled |
On |
RESULT CODES DISPLAY | |
Setting |
SW1/3 |
í Enabled |
On |
Disabled |
Off |
ECHO DISPLAY | |
Setting |
SW1/4 |
í Enabled |
Off |
Disabled |
On |
AUTO ANSWER | |
Setting |
SW1/5 |
í Disabled |
On |
Enabled |
Off |
CARRIER DETECT | |
Setting |
SW1/6 |
í CD normal |
Off |
CD forced high |
On |
SOFTWARE RESET | |
Setting |
SW1/7 |
í CD normal |
Off |
CD forced high |
On |
AT COMMAND SET | |
Setting |
SW1/8 |
Enabled |
On |
Disabled |
Off |
DIAGNOSTIC LED(S) | ||||
LED |
Color |
Status |
Mode |
Condition |
AA |
Red |
On |
Answer |
Auto-answer enabled |
AA |
Red |
Off |
N/A |
Auto-answer disabled |
AA |
Red |
Blinking |
N/A |
Phone is ringing |
CD |
Red |
On |
N/A |
Carrier signal detected |
CD |
Red |
Off |
N/A |
Carrier signal not detected |
RD |
Red |
Blinking |
N/A |
Modem is receiving data or sending result codes |
RD |
Red |
Off |
N/A |
Modem is not receiving data |
SD |
Red |
Blinking |
N/A |
Modem is transmitting data |
SD |
Red |
Off |
N/A |
Modem is not transmitting data |
TR |
Red |
On |
N/A |
DTR signal is high |
TR |
Red |
Off |
N/A |
DTR signal is low |
CS |
Red |
On |
N/A |
CTS high |
CS |
Red |
Off |
N/A |
CTS normal |
ARQ/FAX |
Red |
On |
Data |
Error control connection established |
ARQ/FAX |
Red |
Blinking |
Data |
Error control data is being transmitted |
ARQ/FAX |
Red |
Blinking |
Fax |
Modem is connected in FAX mode |
Proprietary AT Command Set
BIT-MAPPED REGISTER S13 | |||
Format: |
AT [cmds] S13=n [cmds] | ||
Example: |
ATS13=13 <CR> | ||
Default: |
0 | ||
Range: |
0 - 89 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls DTR reset, DTR dialing, reset dialing, and MNP3. | ||
Bit |
Value |
Function | |
0 |
í 01 |
DTR normal. Reset on low DTR. | |
1 |
í 0 |
Not used. | |
2 |
í 0 |
Not used. | |
3 |
í 01 |
DTR dialing disabled. DTR dialing enabled. | |
4 |
í 01 |
Reset dialing disabled. Reset dialing enabled. | |
5 |
í 0 |
Not used. | |
6 |
í 01 |
MNP 3 enabled. MNP 3 disabled. | |
7 |
í 0 |
Not used. |
BIT-MAPPED REGISTER S15 | |||
Format: |
AT [cmds] S15=n [cmds] | ||
Example: |
ATS15=13 <CR> | ||
Default: |
0 | ||
Range: |
0 - 56 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls non-error-correcting mode buffer, MNP4, and BS/DEL switch. | ||
Bit |
Value |
Function | |
0 |
í 0 |
Not used. | |
1 |
í 0 |
Not used. | |
2 |
í 0 |
Not used. | |
3 |
í 01 |
Non-error-correcting mode transmit buffer set to 1.5KB. Non-error-correcting mode transmit buffer set to 128 bytes. | |
4 |
í 01 |
MNP 4 enabled. MNP 4 disabled. | |
5 |
í 01 |
Use backspace key for delete disabled. Use backspace key for delete enabled. |
BIT-MAPPED REGISTER S27 | |||
Format: |
AT [cmds] S27=n [cmds] | ||
Example: |
ATS27=139 <CR> | ||
Default: |
0 | ||
Range: |
0 - 191 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls V.21, V.32 encoding and modulation, V.42 answer tone and handshake, and 9600 result codes. | ||
Bit |
Value |
Function | |
0 |
í 01 |
V.21 disabled. V.21 enabled. | |
1 |
í 01 |
V.32 trellis coding disabled. V.32 trellis coding enabled. | |
2 |
í 01 |
V.32 modulation enabled. V.32 modulation disabled. | |
3 |
í 01 |
2100Hz answer tone enabled. 2100Hz answer tone disabled. | |
5, 4 |
í 0001 10 11 |
V.42 detect, LAPM and MNP enabled. V.42 detect and LAPM enabled. MNP enabled. LAPM enabled. | |
6 |
í 0 |
Not used. | |
7 |
í 01 |
Actual result codes displayed. Force 9600 result codes. |
COMPRESSION AND ERROR CORRECTION | |||
Format: |
AT [cmds] S51=n [cmds] | ||
Example: |
ATS51=3 <CR> | ||
Default: |
0 | ||
Range: |
0 - 7 | ||
Unit: |
Bit-mapped | ||
Description: |
Selects compression and error correction for specific modulations. | ||
Bit |
Value |
Function | |
0 |
í 01 |
MNP/V.42 enabled during V.22 operation. MNP/V.42 disabled during V.22 operation. | |
1 |
í 01 |
MNP/V.42 enabled during V.22bis operation. MNP/V.42 disabled during V.22bis operation. | |
2 |
í 01 |
MNP/V.42 enabled during V.32bis operation. MNP/V.42 disabled during V.32bis operation. |
BIT-MAPPED REGISTER S56 | |||
Format: |
AT [cmds] S56=n [cmds] | ||
Example: |
ATS56=139 <CR> | ||
Default: |
0 | ||
Range: |
0 - 223 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls non-linearing coding, TX level deviation, pre-emphasis, pre-coding, shaping, V.34, and V.FC. | ||
Bit |
Value |
Function | |
0 |
í 01 |
Non linearing coding enabled. Non linearing coding disabled. | |
1 |
í 01 |
TX level deviation enabled. TX level deviation disabled. | |
2 |
í 01 |
Pre-emphasis enabled. Pre-emphasis disabled. | |
3 |
í 01 |
Pre-coding enabled. Pre-coding disabled. | |
4 |
í 01 |
Shaping enabled. Shaping disabled. | |
5 |
í 0 |
Not used. | |
6 |
í 01 |
V.34 enabled. V.34 disabled. | |
7 |
í 01 |
V.FC enabled. V.FC disabled. |
BREAK LENGTH | |
Type: |
Register |
Format: |
AT [cmds] S21=n [cmds] |
Example: |
ATS21=20 <CR> |
Default: |
10 |
Range: |
0-255 |
Unit: |
10 ms |
Description: |
Sets the length of error correction mode breaks sent from DCE to DTE in ARQ mode. |
BREAK TYPE | |
Type: |
Configuration |
Format: |
AT [cmds] &Yn [cmds] |
Example: |
AT &Y0 <CR> |
Description: |
Configures action of break signal. |
Command |
Function |
&Y0 |
Break empties buffer. |
í &Y1 |
Break empties buffer and is sent immediately. |
&Y2 |
Break does not empty buffer and is sent immediately. |
CONNECTION SPEED UPPER LIMIT | |
Type: |
Configuration |
Format: |
AT [cmds] &Nn [cmds] |
Example: |
AT &N1 DT555-1212 <CR> |
Description: |
Sets required connection speed if &U is set to 0. Otherwise, sets fastest allowed connection speed. |
Command |
Function |
í &N0 |
Variable. |
&N1 |
300bps |
&N2 |
1200bps |
&N3 |
2400bps |
&N4 |
4800bps |
&N5 |
7200bps |
&N6 |
9600bps |
&N7 |
12Kbps |
&N8 |
14.4Kbps |
&N9 |
16.8Kbps |
&N10 |
19.2Kbps |
&N11 |
21.6Kbps |
&N12 |
24Kbps |
&N13 |
26.4Kbps |
&N14 |
28.8Kbps |
CONNECTION SPEED LOWER LIMIT | |
Type: |
Configuration |
Format: |
AT [cmds] &Un [cmds] |
Example: |
AT &U1 DT555-1212 <CR> |
Description: |
Sets slowest allowed connection speed if &N is set to 1 or higher. |
Command |
Function |
í &U0 |
Disabled. |
&U1 |
300bps |
&U2 |
1200bps |
&U3 |
2400bps |
&U4 |
4800bps |
&U5 |
7200bps |
&U6 |
9600bps |
&U7 |
12000bps |
&U8 |
14400bps |
&U9 |
16800bps |
&U10 |
19200bps |
&U11 |
21600bps |
&U12 |
24000bps |
&U13 |
26400bps |
&U14 |
28800bps |
ERROR CONTROL MODE | |
Type: |
Configuration |
Format: |
AT [cmds] &Mn [cmds] |
Example: |
AT &M1 %C1 <CR> |
Description: |
Selects active error-control protocols. |
Command |
Function |
&M0 |
Normal mode, error control disabled. |
í &M4 |
Normal/ARQ. |
&M5 |
ARQ mode. |
ESCAPE CHARACTER RESPONSE | |
Type: |
Register |
Format: |
AT [cmds] S14=n [cmds] |
Example: |
ATS14=0 <CR> |
Default: |
0 |
Description: |
Controls reaction to escape character. |
Command |
Function |
í S14=0 |
Normal operation. |
S14=1 |
When +++ is received, modem goes on hook, enters command state and sends NO CARRIER result code. |
EXTENDED RESULT CODES | |
Type: |
Configuration |
Format: |
AT [cmds] &An [cmds] |
Example: |
AT &A1 %C1 <CR> |
Description: |
Selects extended result codes. |
Command |
Function |
&A0 |
Extended result codes disabled. |
&A1 |
ARQ result codes enabled. |
&A2 |
V.32 result code enabled. |
í &A3 |
Error correction and compression result codes enabled. |
FLOW CONTROL CHARACTER - XON | |
Type: |
Register |
Format: |
AT [cmds] S22=n [cmds] |
Example: |
ATS22=20 <CR> |
Default: |
17 |
Range: |
0-127 |
Unit: |
ASCII |
Description: |
Sets the character used to represent XON. |
FLOW CONTROL CHARACTER - XOFF | |
Type: |
Register |
Format: |
AT [cmds] S23=n [cmds] |
Example: |
ATS23=20 <CR> |
Default: |
19 |
Range: |
0-127 |
Unit: |
ASCII |
Description: |
Sets the character used to represent XOFF. |
FLOW CONTROL PASSTHROUGH | |
Type: |
Configuration |
Format: |
AT [cmds] &In [cmds] |
Example: |
AT &I0 &W <CR> |
Description: |
Allows modem to act on, then transmit XON/XOFF characters. |
Command |
Function |
í &I0 |
Software flow control disabled. |
&I1 |
XON/XOFF passthrough enabled. |
&I2 |
XON/XOFF passthrough disabled. |
FLOW CONTROL TYPE | |
Type: |
Configuration |
Format: |
AT [cmds] &Hn [cmds] |
Example: |
AT &H0 A <CR> |
Description: |
Sets type of flow control used by modem. |
Command |
Function |
&H0 |
Flow control disabled. |
í &H1 |
CTS/RTS flow control enabled. |
&H2 |
XON/XOFF flow control enabled. |
&H3 |
CTS/RTS and XON/XOFF flow control enabled. |
HELP SCREENS | |
Type: |
Immediate |
Format: |
AT <prefix>$ |
Example: |
AT &$ <CR> |
Description: |
Shows command help screens for all commands beginning with the given prefix, or no prefix if none is given. |
Command |
Function |
$ |
Shows AT help screen. |
&$ |
Shows AT& help screen. |
INACTIVITY TIMER | |
Type: |
Register |
Format: |
AT [cmds] S19=n [cmds] |
Example: |
ATS19=20 <CR> |
Default: |
0 |
Range: |
Unidentified |
Unit: |
1 minute |
Description: |
Sets the length of time that the modem does not receive information before it disconnects. |
LOCK SERIAL PORT | |
Type: |
Configuration |
Format: |
AT [cmds] &Bn [cmds] |
Example: |
AT &N9 &B0 <CR> |
Description: |
Sets operation of serial port speed. |
Command |
Function |
&B0 |
Serial speed follows connect speed. |
í &B1 |
Serial speed locked. |
&B2 |
Serial speed locked in ARQ mode only. |
MAPPING | |||
Format: |
AT [cmds] S55=n [cmds] | ||
Example: |
ATS55=13 <CR> | ||
Default: |
0 | ||
Range: |
0 - 15 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls mapping. | ||
Bit |
Value |
Function | |
0 |
í 01 |
8S-2D map enabled. 8S-2D map disabled. | |
1 |
í 01 |
16S-4D map enabled. 16S-4D map disabled. | |
2 |
í 01 |
32S-2D map enabled. 32S-2D map disabled. | |
3 |
í 01 |
64S-4D map enabled. 64S-4D map disabled. |
REPORT INFORMATION | |
Type: |
Immediate |
Format: |
AT [cmds] In [cmds] |
Example: |
AT I1 O <CR> |
Description: |
Displays modem properties. |
Command |
Function |
I0 |
Reports product code. |
I1 |
Reports ROM checksum result. |
I2 |
Reports RAM checksum result. |
I3 |
Reports firmware version. |
I4 |
Reports current command settings. |
I5 |
Reports current NVRAM settings. |
I6 |
Reports current connections statistics. |
I7 |
Reports configuration. |
BAUD RATE | |||
Format: |
AT [cmds] S54=n [cmds] | ||
Example: |
ATS54=139 <CR> | ||
Default: |
0 | ||
Range: |
0 - 255 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls baud rate. | ||
Bit |
Value |
Function | |
0 |
í 01 |
2400 baud rate enabled. 2400 baud rate disabled. | |
1 |
í 01 |
2743 baud rate enabled. 2743 baud rate disabled. | |
2 |
í 01 |
2800 baud rate enabled. 2800 baud rate disabled. | |
3 |
í 01 |
3000 baud rate enabled. 3000 baud rate disabled. | |
4 |
í 01 |
3200 baud rate enabled. 3200 baud rate disabled. | |
5 |
í 01 |
3429 baud rate enabled. 3429 baud rate disabled. | |
6 |
í 01 |
Call indicate during V.34 operation enabled. Call indicate during V.34 operation disabled. | |
7 |
í 01 |
V.8 during V.34 operation enabled. V.8 during V.34 operation disabled. |
TONE DIALING TEST | |
Type: |
Register |
Format: |
AT [cmds] S16=n [cmds] |
Example: |
ATS16=1 <CR> |
Description: |
Selects the tone dialing test |
Command |
Function |
í S16=0 |
Tone dialing test disabled. |
S16=1 |
Tone dialing test enabled. |
V.32 AND V.32bis MODULATIONS | |||
Format: |
AT [cmds] S34=n [cmds] | ||
Example: |
ATS34=13 <CR> | ||
Default: |
6 | ||
Range: |
0 - 15 | ||
Unit: |
Bit-mapped | ||
Description: |
Controls V.32 and V.32bis modulations. | ||
Bit |
Value |
Function | |
0 |
í 01 |
V.32bis enabled. V.32bis disabled. | |
1 |
í 1 |
Not used. | |
2 |
í 1 |
Not used. | |
3 |
í 01 |
V.32 modulation disabled. V.32 modulation enabled. |
V.32 HANDSHAKE TIME | |
Type: |
Register |
Format: |
AT [cmds] S28=n [cmds] |
Example: |
ATS28=20 <CR> |
Default: |
8 |
Range: |
0-255 |
Unit: |
.1 second |
Description: |
Sets length of V.32 handshake. |