Modem AT Commands, S Registers and RS-232C pins

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| Modem AT Command | S Registers | RS-232C pin assignments |

AT	Options / Details	Chipset / Protocol
+++	Escape Code	All
A/	Repeat Last Command	All
A>	Continuously Repeat Command	USR
AT	Command Mode Prefix	All
AT#CID=n	n=0 Disable caller ID n=1 Enable caller ID in readable format n=2 Enable caller ID in HEX format	Must have feature #142. Type ATi10
AT$	HELP, Command Summary	USR
AT%Cn	n=0 Data compression disable n=1 MNP5 enable n=2 V.42 enable n=3 V.42bis and MNP5	V.34, Rockwell, Compression selection
AT%En	n=0 Do not request retrain n=1 Enable monitoring and retraining if line is bad n=2 Enable monitoring and retraining if line is bad, wait one minute before renogotiating higher speed	V.32 retraining
AT%Fn	n=1 Select 75Tx/1200Rx n=2 Select 100Tx/75Rx n=3 Select V.23 half-duplex	Optional feature #121. Data echo options
AT%Gn	n=0 Disable V.32bis rate negotiation n=1 Enable V.32bis rate negotiation	V.32 Initiation of rate renegotiation
AT%L	Report received signal level 009=-9 dBm (or more) 010=-10 dBm etc. 043=-43 dBm (or less)	Rockwell. Returns value representing signal level in -dBm. The smaller the number, the better the connection.
AT%Q	Report line signal quality Range of 0-128	Rockwell. Lower the number, better the line. Reading is instantanteous, repeat serveral times for acurate reading.
AT&$	HELP, Ampersand Commands	USR
AT&An	n=0 Disable /ARQ Result Codes n=1 Enable /ARQ Result Codes n=2 Enable /Modulation Codes n=3 Enable /Extra Result Codes	Result codes-All
AT&Bn	n=0 Floating DTE Speed n=1 Fixed DTE Speed n=2 DTE Speed Fixed When ARQ	DTE speed variables
AT&Cn	n=0 DCD Always On n=1 Modem Controls DCD	Data Carrier Detect
AT&Dn	n=0 Ignore DTR n=1 On-Line Command Mode n=2 DTE Controls DTR n=3 Reset modem (ATZ)	Select modem reaction to DTR. Works with &Q command
AT&Fn	n=0 Load Factory 0, no FC n=1 Load Factory 1, HW FC n=2 Load Factory 2, SW FC	Load Factory Default
AT&Gn	n=0 No Guard Tone n=1 550 Hz Guard Tone n=2 1800 Hz Guard Tone	Guard Tone
AT&Hn	n=0 Disable TX Flow Control n=1 CTS n=2 Xon/Xoff n=3 CTS and Xon/Xoff	USR, serial port flow control
AT&In	n=0 Disable RX Flow Control n=1 Xon/Xoff n=2 Xon/Xoff Chars Filtered n=3 HP Enq/Ack Host Mode n=4 HP Enq/Ack Terminal Mode n=5 Xon/Xoff for non-ARQ Mode	USR, serial port flow control
AT&Kn	n=0 Disable Data Compression n=1 Auto Data Compression n=2 Enable Data Compression n=3 Selective Data Compression	USR, data compression control
AT&Kn	n=0 Disable flow control n=3 Enable bi-directional hardware (RTS/CTS) flow control n=4 Enable software (XON/XOFF) n=5 Enable trnasparent flow control n=6 Enable both hardware and software flow control	Rockwell, serial port flow control
AT&Mn	n=0 Normal Mode n=4 ARQ/Normal Mode n=5 ARQ Mode	USR Asynchronous/Synchnous mode
AT&Nn	n=0 Highest Link Speed n=1 300 bps n=2 1200 bps n=3 2400 bps n=4 4800 bps n=5 7200 bps n=6 9600 bps n=7 12000 bps n=8 14400 bps n=9 16800 bps n=10 19200 bps n=11 21600 bps n=12 24000 bps n=13 26400 bps n=14 28800 bps n=15 31200 bps n=16 33600 bps	USR
AT&Pn	n=0 N.American Pulse Dial n=1 UK Pulse Dial	USR pulse dial selection
AT&Pn	n=0 N.American Pulse Dial (39%/61% and 10PPS) n=1 UK/Hong Kong Pulse Dial (33%/67% and 10PPS) n=2 39%/61% and 20PPS n=3 33%/67% and 20 PPS (Japan)	Rockwell make/break ratio for pulse dial
AT&Q	n=1 Synch mode 1 n=2 Synch mode 2, dial stored number when DTR makes transition n=3 Synch mode 3, manual dialing n=4 Reserved n=5 Reliable Asynch mode n=6 Normal Asynch mode	Rockwell asynch/synch mode Same as &M, depending on &F
AT&Rn	n=1 Ignore RTS n=2 RX to DTE/RTS high	USR
AT&Sn	n=0 DSR Always On n=1 Modem Controls DSR	USR
AT&Tn	n=0 End Test n=1 Analog Loopback (ALB) n=3 Digital Loopback (DLB) n=4 Grant Remote DLB n=5 Deny Remote DLB n=6 Remote Digital Loopback n=7 Remote DLB With Self Test n=8 ALB With Self Test	USR
AT&Un	n=0 Variable link rate floor. n=1 Minimum link rate 300 bps n=2 Minimum link rate 1200 bps n=3 Minimum link rate 2400 bps n=4 Minimum link rate 4800 bps n=5 Minimum link rate 7200 bps n=6 Minimum link rate 9600 bps n=7 Minimum link rate 12000 bps n=8 Minimum link rate 14400 bps n=9 Minimum link rate 16800 bps n=10 Minimum link rate 19200 bps n=11 Minimum link rate 21600 bps n=12 Minimum link rate 24000 bps n=13 Minimum link rate 26400 bps n=14 Minimum link rate 28800 bps n=15 Minimum link rate 31200 bps n=16 Minimum link rate 33600 bps	USR
AT&V	Display configuration information	Rockwell
AT&Wn	n=0 Store Configuration 0 n=1 Store Configuration 1	All
AT&Yn	n=0 Destructive n=1 Destructive/Expedited n=2 Nondest./Expedited n=3 Nondest./Unexpedited	All
AT&Zn=s	Store Phone Number	All
AT&Zn?	Query Phone Number
AT)Mn	n=0 Adust transmit level if remote is set to )M1, otherwise -10 dBm n=1 Will try to adust power leve to less than -10 dBm with MNP 10	Optional feature #144. Transmit level adjustment for cellular connection.
AT*B	Display blacklisted numbers as defined by country requirements.	optional feature #123. Used by countries that have permanently forbidden numbers.
AT*C	Set configuration password	Optional feature #124
AT*E	Exit secure access remote configuration	Optional feature #124
AT*Hn	n=1 Negotiate at highest supported speed n=2 Negotiate link at 1200bps n=3 Negotiate link at 4800bps	Link Negotiation Rate
AT*L	List callback security passwords	Optional feature #124
AT*NC?	Display country specific configurations	Optional feature #120
AT*NCn	n=ID of specific country	Optional feature #120
AT*Pn:word:	n=0-19 passwords and tel. numbers	Optional feature #124
AT*R	Activate remote configuration mode.	Optional feature #124, works with *C
AT*R	Request secure access mode	Optional feature #124
AT+FAA=n	n=2 Activate silent answer for class 2 fax n=4 Activate silent answer plus for class 2 fax
AT+FAE=n	n=1 Activate Adaptive Answer n=3 Activate silent answer for class 1 fax
AT+MS	Modulation control ,,,	V.34 only
AT+MS=	n=0 Automode Disabled n=1 Automode enable using V.8 or V.32bis Annex A	V.34 only. Automode does not work with Bell 212
AT+MS=	28800,26400 etc. default for V.34 is 28800	V.34 only
AT+MS=	300,1200,2400 etc. default for V.34 is 300bps	V.34 only
AT+MS=	n=0 V.21, 300bps n=1 V.22, 1200bps n=2 V.22bis, 1200/2400 n=3 V.23 bisynch 75/1200 n=9 V.32, 4800/9600 n=10 V.32bis, 4800/7200/9600/12000/ 14400 n=11 V.34, 2400/4800/7200/9600/ 12000/14400/16800/ 19200/24000/26400/ 28800 n=64 Bell 103, 300bps n=69 Bell 212, 1200bps n=74 V.FC, 14400/16800/ 19200/24000/26400/ 28800	V.34 only
AT+MS?	Reports MS options	V.34 only
AT-B	Forced fallback to 1200	Optional feature #143
AT-Cn	n=0 MNP 10 enabled, sync mode n=1 MNP 10 enabled, asynch mode n=2 MNP 2 enabled n=3 MNP 3 enabled	Optional feature #143
AT-Kn	n=0 Do not convert LAPM to MNP n=1 Convert LAPM connection to MNP 10 n=3 Enable MNP 10 extended services detection	Optional feature #143
AT-Qn	n=0 Enable fallback to V.22/V.22bis n=1 Disable fallback	Optional feature #143
AT-Un	n=0 Allow attenuation to -10 dBm n=1 Allow attenuation to -18 dBm n=2 Allow attenuation to -22 dBm n=3 Allow attenuation to -25 dBm n=4 Force 2400 bps transmit level to -10 dBm n=5 Force 2400 bps transmit level to -18 dBm n=6 Force 2400 bps transmit level to -22 dBm n=7 Force 2400 bps transmit level to -25 dBm	Optional feature #143. Forced transmit level change during fall forward
ATA		Hayes - Answer Phone Line
ATBn	n=0 V32/CCITT 1200b[s n=1 Bell Standard 212A 1200bps n=2 V.23 originate: T75/R1200 when DTE speed is 1200 bit/second. V.23 answer: T75/R1200 when DTE speed is 1200 bit/second. n=3 - V.23 originate: T1200/R75 when DTE speed is 1200bps. V.23 answer: T1200/R75 when DTE speed is 1200BPS. n=6 V.26 bis when line speed is 1200bps n=15 V.21 when line speed is 300bps n=16 Industry Standard 103 when speed is 300 bps. n=30 V.22 bis when speed is 2400bps n=32 V.26 bis when speed is 2400bps n=41 V.32 when line speed is 4800bps n=52 V.32 bis when speed is 7200bps n=60 V.32 when speed is 9600bps n=64 V.FC when speed is 9600bps n=70 V.32 bis when handshake begins at 12000 bps. n=71 V.FC when handshake begins at 12000 bit/second. n=75 - V.32 bis when handshake begins at 14400 bit/second. n=76 - V.FC when handshake begins at 14400 bit/second. n=81 - V.FC when handshake begins at 16800-28800 bit/second.	Hayes - Communications options
ATD$	HELP, Dial Commands	USR
ATDL	Dial Last Phone Number	USR/Rockwell
ATDn	Dial a Telephone Number n=0..9#*TPR,;W@!()-	All
ATDSn	Dial Stored Phone Number	USR/Rockwell
ATEn	n=0 No Command Echo n=1 Echo Command Chars	All
ATFn	n=0 Online Echo n=1 No Online Echo	USR
ATFn	n=0 Best possible auto-detect, same as ATN1 n=1 V.21 or Bell 102 300bps n=3 V.23 n=4 V.22 or Bell 212A 1200bps n=5 V.22bis 2400bps n=6 V.32bis or V.32 4800bps n=7 V.32bis 7200bps n=8 V.32bis or V.32 9600bps n=9 V.32bis 12,000bps n=10 V.32bis 14,400bps n=13 V.FC 14,400 n=14 V.FC 16,800 n=15 V.FC 19,200 n=16 V.FC 21,600 n=17 V.FC 24,000 n=18 V.FC 26,400 n=19 V.FC 28,800	Rockwell, only used by V.FC modems Clears register S31 bit 1. F13 and F19 reccommend connection rate.
ATHn	n=0 On Hook (Hang Up) n=1 Off Hook
Ati10 results	Optional Features: 101=Class 1 fax 104=Class 2 fax (TR29.2) 105=Class 2.0 fax (ITU-TSS) 115=V.17 14.4k FAX 120=WorldWide support 121=V.23 122=V.25bis 123=Blacklisting (B and d commands) 124=Access Security 140=V.32bis 14.4k DATA 141=Silent Answer [fax feature] 142=Caller ID 143=MNP 10 144=MNP Cellular 145=AutoSync 146=Enhanced Config Display (\S) 147=V.FC 28k 148=Volume Control L+/L- 149=V.FC 24k	Optional Features cont. 150=Enhanced &F option 151=Enhanced Rate Renogotiation 153=ITU-TSS V.34 28.8 154=Silent Answer Plus 157=RINGING response 160=Supra Voice Porcession 161=Supra Voice Porcession 162=Supra Voice Porcession 170=Handset support 171=Headset Support 180=16550 UART emulation 181=SupraSmart UART 182=Rockwell high speed interface 190=AMD flash ROM 191=ATMEL flash ROM
ATIn	n=0 Product Code n=1 Checksum n=2 RAM Test n=3 Product ID string n=4 Current Settings n=5 NVRAM Settings n=6 Link Diagnostics n=7 Product Configuration n=10 Optional features [fax, etc., see end]
ATL+/-n	+n=1-32 Increases speaker volume -n=1-32 Decreases speaker volume	Relative Speaker Volume-Optional feature #148
ATLn	n=0 Low Speaker Volume n=1 Low Speaker Volume n=2 Med Speaker Volume n=3 Hi Speaker Volume
ATMn	n=0 Speaker Off n=1 Speaker On Until CD n=2 Speaker Always On n=3 Speaker Off During Dial
ATNn	n=0 Use rate in S37 n=1 Use highest possble rate	Connection Rate
ATOn	n=0 Return Online n=1 Return Online & Retrain
ATP	Pulse Dial
ATQn	n=0 Result Codes Sent n=1 Quiet (No Result Codes) n=2 Verbose/Quiet On Answer
ATT	Tone Dial
ATVn	n=0 Numeric Responses n=1 Verbal Responses
ATWn	n=0 Not reported, DTE rate shown n=1 Result reported n=2 Not reported, DCE rate shown	Error Correction Result Codes
ATXn	n=0 Basic Result Codes n=1 Extended Result Codes n=2 Wait for tone before dialing n=3 Ignore dial tone n=4 Wait for tone, detect dialtone and report busy
ATYn	n=0 Next reset to &W0 settings n=1 Next reset to &W1 settings Internal Only n=2 Next Reset to &F0 settings n=3 Next Reset to &F1 settings n=3 Next Reset to &F1 settings
ATZn	n=0 Dipswitch #7 determines reset n=1 Reset to &W0 settings n=2 Reset to &W1 settings n=3 Reset to &F0 settings n=4 Reset to &F1 settings n=5 Reset to &F2 settings	Dipswitch is USR only
AT\Nn	n=0 Normal connection using flow control n=1 Direct connection, no flow control n=2 LAPM/MNP 5,4,3, 2 (Reliable) n=3 Autoreliable mode (LAPM or MNP) n=4 LAPM reliable mode n=5 MNP reliable mode	Operating Mode
AT\S	Display configuration information	Optional feature #146.

S Registers

S Registers	Options	Details
S000=n	n=1-255, number of rings before the modem answers a call
S001	Ring counter, range=0-255
S002=n	Escape code, range=0-255	default=43 "+". Anything greater than 127 disables escape
S003=n	range=0-127, default is 13	Carriage Return
S004=n	range 0-127, default is 10	Line feed
S005=n	range 0-32, default is 8	Backspace
S006=n	range 2-255, default 2 or 4	Time to wait to blind dial, units=seconds
S007=n	range 1-255, default=2	Time to wait for carrier, units=seconds
S008=n	range=0-255, default=2	Pause time for comma, units=seconds
S009=n	range=1-255, default=6	Time to wait before recognizing carrier units=1/10 seconds
S010=n	range=1-255, default=14	Delay from lost carrier to hang up units=1/10 seconds
S011=n	range=50-255, default= 70 or 95	DTMF tone duration/spacing units=1/1000 seconds
S012=n	range=0-255, default=5	Escape code guard time units =1/100 seconds
S018=n	Range: 0-255 seconds, Default: 0	Test Timer. Sets the length of time, in seconds, that the modem conducts a test (commanded by &Tn) before returning to the command mode. If this register value is zero, the test will not automatically terminate; the test must be terminated from the command mode by issuing an &T0 or H command. When S18 is non-zero, the modem returns the OK message upon test termination.
S025=n	range=0-255, default=1	Delay to DTR, units=1/100 seconds
S026=n	range=0-255, default=5	RTS to CTS delay, units=1/100 seconds
S030=n	range=0-255, default=0	Disconnect inactivity timer units=tens of seconds
S032=n	range=0-255, default=19	XON charachter
S033=n	range=0-255, default=19	XOFF charachter
S036=n	n=0 Disconnect n=1 Establish a direct connection n=3 Establish a normal connection n=4 Establish an MNP connection if possible, otherwise direct n=5 Establish an MNP connection if possible, otherwise normal	Negotiation failure treatment
S037=n	n=0 Rate of last AT command issue, or modem default (maximum) n=1 300bps n=5 1200bps n=6 2400bps n=8 4800bps n=9 9600bps n=10 12,000bps n=11 14,400bps n=12 28,800bps	Desired line speed. Ignored unless N=0, overridden by +MS setting.
S038=n	range=0-255, default=20	Delay before forced disconnect units=seconds
S046=n	n=136 Compression disabled n=138 Compression enabled	Protocol selection
S048=n	n=0 Disable V.42, proceed with LAPM n=7 Enable V.42 n=128 Disable V.42, look to S36	V.42 negotiation
S080=n	n=0-31Reserved n=32 V.25 commands only n=64 Remote configure enable n=128 Callback security enable	V.25 only, optional feature #120 default=1. Settings are bit values expressed in decimal
S086=n	n=0 Normal disconnect, no error n=4 Loss of carrier n=5 V.42 negotiation failed n=9 Modems could not find common protocol n=12 Normal disconnect initiated by remote modem n=13 Remote modem did not respond after 10 re-transmissions n=14 Protocol violation	Connection failure cause code register
S095=n	n=0 CONNECT XXXX shows DCE n=1 Append/ARQ to verbose code if protocol is not NONE n=2 Enable CARRIER XXXX result n=3 Enable PROTOCOL XXXX result n=4 Reserved n=5 Enable COMPRESSION result n=6 Reserved n=7 Enable RINGING response	V.34 Rockwell Extended result codes
S091=n		PSTN transit level
S095=n	n=0 Disable COMPRESSION XXXX n=32 Enable result code	USR Result code commands
S109=n	n=1 reserved n=2 4800bps n=4 7200bps n=8 9600bps n=16 12000 bps n=32 14400 bps n=64 reserved n=128 reserved	V.32 & V.32bis range of available modem speeds. Lowest speed to start of training/ negotiation.
S110=n	n=0 V.32 no rate adjustment n=1 V.32/V.32bis no rate adjustment n=2 V.32/V.32bis with rate adjustment n=3 start negotiation at lowest possible speed as set in +MS command n=14 V.34, V.FC, V.32bis with rate adjustment	V.32, V.32bis and V.FC rate adjustment options
S201=n	n=0 initial power setting n=5 Compromise equalizer enable n=6 Reserved n=7 Reserved	Cellular transmit level
Sr=n	Sets Register "r" to "n"
Sr?	Query Register "r"

RS-232C pin assignments

Pin	EIA	Abbrev.	Source	Description
1	AA	sheild	n/a	protective ground
2	BA	TXD	DTE	transmit data
3	BB	RXD	DCE	receive data
4	CA	RTS	DTE	request to send
5	CB	CTS	DCE	clear to send
6	CC	DSR	DCE	data set ready
7	AB	GND	n/a	signal ground
8	CF	DCD	DCE	data carrier detect
12	CI	SI	DCE	data speed indicator
15	DB	TCLK	DCE	transmit clock, sync only
17	DD	RCLK	DCE	receive clock, sync only
20	CD	DTR	DTE	data terminal ready
22	CE	RI	DCE	ring indicator
23	CI	SI	DCE	data signal rate selector
24	DA	XTCLK	DTE	external transmit clock, sync only

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