APPENDIX B. SUMMARIES AND TABLES CONTENTS The RS-232 Interface, with Pin Definitions Front Panel Indicators DIP Switch Summary Default Settings S-Register Summary ASCII Chart THE RS-232 INTERFACE DESCRIPTION The RS-232 interface is a standard developed by the Electronic Industries Association (EIA). It defines the signals and voltages used when data is exchanged between a computer or terminal and a modem or serial printer. Data is transmitted between the devices via a cable with 25-pin, 9-pin, 8-pin or custom-built connectors. PIN ASSIGNMENTS The entire standard covers many more functions than are used in most data communications applications. Pin assignments are factory set in the Courier to match the standard DB-25 assignments in the following table. DB- 9 connectors for AT-compatible computers should be wired at the computer end of the cable as shown in the DB-9 column. If you're using an Apple computer, ask your dealer for the correct modem cable for your Apple computer model. Signal Flow DB-25 DB-9 Circuit Function D TE ê DCE* 1 ê AA Chassis Ground both directions 2 3 BA Transmitted Data to DCE 3 2 BB Received Data to DTE 4 7 CA Request to Send to DCE 5 8 CB Clear to Send to DTE 6 6 CC Data Set Ready to DTE 7 5 AB Signal Ground both directions 8 1 CF Carrier Detect to DTE 12 ê SCF Speed Indicate to DTE 15 ê DB Synchronous TX** Timing t o DTE 17 ê DD Synchronous RX** Timing t o DTE 20 4 CD Data Terminal Ready to DCE 22 9 CE Ring Indicate to DTE 24 ê DA Synchronous TX** Timing t o DCE * DTE indicates the terminal or computer; DCE indicates the modem. ** Indicates Transmitter (TX) or Receiver (RX) RS-232 Interface Pin Definitions Minimum Requirements Some computer/terminal equipment supports only a few of the RS-232 signal functions set in the Courier. The minimum required for the modem to operate are as follows: Asynchronous Calls DB-25 DB-9 Pin Pin Function 2 3 Transmitted Data 3 2 Received Data 7 5 Signal Ground 20 4 Data Terminal Ready* * Required only if you have the Data Terminal Ready Override switch OFF (DIP switch 1 UP). Synchronous Calls You will need all of the above functions as well as pin 15 for Transmitter timing signals, and pin 17 for Receiver timing signals. You may need pin 24, which is assigned the external timing source, rather than the internal (modem) source assigned to pin 15. See Chapter 7 for more detailed information. Additional Flow Control Functions If your computer and software support Clear to Send and you wish to use Transmit Data hardware flow control (&H1), Pin 5 (DB-25) or Pin 8 (DB-9) is required. If your computer and software support Request to Send and you wish to use Received Data hardware flow control (&R2), Pin 4 (DB-25) or Pin 7 (DB-9) is required. FOR 38.4K DTE RATE OR HIGHER Your terminal or computer and software must support the 38.4K rate. Make sure the RS-232 cable is shielded. Cables are normally six feet long, but longer lengths are possible. If you encounter problems with signal degradation, try a shorter cable. If you decide to build your own cable, use a low-capacitance cable. To further minimize the capacitance, connect only those functions (pins) that your application requires. FRONT PANEL INDICATORS SymbolMeaning Status HS High Speed All calls above 2400 bps: ON during call progress, after completion of dialing; OFF during HST-mode link negotiations at 2400 bps, then ON during connection. Remains ON after disconnect until next call is originated or answered. AA Auto Answer/ Answer mode only: ON when your modem is Answer in Auto Answer mode, and when answering a call; in HST mode, goes OFF if the channel is reversed and your answering modem transmits at 450 or 300 bps. Also goes OFF when the modem originates a call. CDCarrier Detect ON if DIP switch 6 is UP (factory setting) and the Courier receives a valid data signal (carrier) from a remote modem, indicating that data transmission is possible. Also ON when the CD override is on, DIP switch 6 DOWN. OH Off Hook ON when the Courier takes control of the phone line to establish a data link. RDReceived Data Flashes when the modem sends result codes or passes received data bits to the computer or terminal. SD Send Data Flashes when the computer or terminal sends a data bit to the Courier. TRData Terminal ON if DIP switch 1 is UP (factory setting) and Ready the modem receives a DTR signal from the computer or terminal. Also ON when the DTR override is on, DIP switch 1 DOWN. MR Modem Ready/ ON when the Courier is powered on. Test Mode Flashes when the modems retrain, including online fallback, or while the modem is in Test mode. SymbolMeaning Status RS Request to ON if your terminal or software supports RTS Send and sends the RTS signal. OFF if the Courier is set to &R2 (Received Data hardware flow control) and the computer or terminal lowers RTS. CSClear to Send ON until the modem lowers CTS when Transmit Data hardware flow control is enabled (&H1, &H3). Always ON during synchronous connections. SYN Synchronous ON when the modem is set to &M1 and Mode enters synchronous mode. ARQError Control Automatic Repeat Request. ON when the Courier is set to &M4 or &M5 and successfully connects with another modem under error control. Flashes when the Courier retransmits data to the remote modem. DIP SWITCH SUMMARY PURPOSE The DIP switches, located at the rear of the modem, are for adapting the modem to your equipment and personal require- ments. The quick-configuration guide that comes with the modem indicates the recommended switch settings for many communications software packages. If necessary, review your software documentation. Some users are able to move a single switch with a finger tip. If this doesn't work for you, use a toothpick or other small instrument. OPERATIONS The DIP switch settings are power-on defaults, read by the Courier when it is turned on. If changed when the modem is on, switches 2-5, 7 and 9 require the ATZ (software reset) command to initiate the new settings. If you've set switch 8 UP to disable command recognition, and want to return the modem to Smart mode so that it responds to commands, you'll have to power off the modem, reset switch 8 DOWN, and power on the modem again. The remaining (hardware) switches are automatically operative when set UP or DOWN. Factory SwitchSetting Function 1 OFF Data Terminal Ready Operations OFF Normal DTR operations: computer must provide DTR signal for modem to accept commands; dropping DTR terminates a call ON DTR always ON (Override) 2 OFF Verbal/Numeric Result Codes OFF Verbal (word) results ON Numeric results Factory SwitchSetting Function 3 ON Result Code Display OFF Results suppressed ON Results enabled 4 OFF Command Mode Local Echo OFF Keyboard commands displayed ON Echo suppressed 5 ON Auto Answer OFF Modem answers on first ring ON Auto answer disabled 6 OFF Carrier Detect Operations OFF Courier sends CD signal when it connects with another modem, drops CD on disconnect ON CD always ON (Override) 7 OFF Auxiliary, DIP Switch 3 ON OFF Result codes in Originate and Answer mode ON Result codes in Answer mode disabled 8 ON AT Command Set Recognition OFF Command recognition disabled (Dumb Mode) ON Recognition enabled (Smart mode) 9 OFF Escape Code (+++) Response OFF Modem hangs up, returns to Command mode, sends NO CARRIER result ON Modem maintains connection, returns to Command mode, sends OK result 10 OFF Power-on and ATZ Reset Software Defaults OFF Load from nonvolatile memory (NVRAM) ON Load factory settings from read only memory (ROM) continued Factory SwitchSetting Function QUAD OFF RS-232 Transmit/Receive Pin Assignments SWITCH OFF Normal assignments; see Pin Assignments in Appendix B-1 ON Reversed Transmit/Receive pins The need to change this switch setting is rare. Carefully review your computer or terminal documentation before setting this switch DOWN. DEFAULT SETTINGS USER-PROGRAMMABLE DEFAULTS You can create your own default configuration and store it in nonvolatile random access memory (NVRAM) using the &W command described in Chapter 5. As long as DIP switch 10 is UP when you power on the modem, your defaults are loaded into the modem's random access memory (RAM). To view your NVRAM settings at any time, use the ATI5 command. Tables on the next two pages list the options you can store in NVRAM, including S-Register settings. If DIP switch 10 is DOWN at power-on, the factory settings listed in the table are loaded instead. The first time the modem is turned on, the NVRAM settings are the same as the factory settings. The following command example substitutes several user-defined defaults for factory settings. The modem also stores the rate, word length and parity it detects from the AT command prefix. AT X4 &B1 &M5 &H1 M3 &W NVRAM Options Factory Setting Handshake option B0/B1 V.32 bis mode/HST mode Normal/error control modes &M4 Normal/ARQ Data compression &K1 Auto enable/disable Transmit data flow control &H0 Disabled Rec'd. data hardware flow control &R1 Ignore RTS Rec'd. data software flow control &I0 Disabl ed DTE rate select &B0 Detect from AT command; variable Link rate select &N0 Variable Result code subset X1 Extended Error-control response codes &A1 Enabled Tone/Pulse dialing P Pulse dial Online local echo F1 Disabled Speaker control M1 ON during dial through connect Remote Digital Loopback (RDL) &T5 Deny RDL Normal/Leased line &L0 Normal phone line Data Set Ready override&S0 Enabled Synchronous clock source&X0 Modem transmitter Break handling &Y1 Clear buffer, send immediately Stored telephone number&Z0-3=0 Blank Pulse dial make/break ratio &P0 U.S./Canada Guard tone &G0 U.S./Canada Rack Controller Unit (RCU) Access %R0 RCU access disabled Word length* 7 Parity* 1 Even DTE rate* 19.2K * Detected by the modem from the AT prefix of the &W command that writes your defaults to NVRAM. Set your software to the desired word length, parity, and DTE rate defaults before sending the modem the AT . . . &W string. Factory NVRAM S-Register Options Setting S2 Escape code character 43 S3 Carriage Return character13 S4 Line Feed character 10 S5 Backspace character 8 S6 Dial wait-time, sec. 2 S7 Carrier wait-time, sec. 60 S8 Dial pause, sec. 2 S9 Carrier Detect time, 1/10th sec. 6 S10Carrier loss wait-time, 1/10th sec. 7 S11Touch-Tone duration, spacing, msec. 70 S12Escape code guard time, 1/50th sec. 50 S13 Bit-mapped functions 0 S15 Bit-mapped functions 0 S19 Inactivity/hang up timer 0 S21Break length, 1/100th msec. 1 0 S22 XON character 1 7 S23 XOFF character 1 9 S24Pulsed DSR duration, 2/100th sec. 150 S26RTS/CTS delay time, 1/100th sec. 0 S27 Bit-mapped functions 0 S28V.32 handshake time, 1/10th sec. 8 S32 Talk/Data Switch Options 1 S34 Bit-mapped functions 0 S38 Disconnect wait time, sec. 0 * Bit-mapped registers have up to eight functions. See Appendix B-5 in the manual or the briefer summary in the Quick Reference Card. S-REGISTER SUMMARY USAGE The default values are those users typically require. Change the settings with the ATSr=n command, where r is the register and n is a decimal value from 0-255: ATS13=8 The modem does not perform a value-range check. Some values you select may not work with some equipment, and you'll have to readjust the settings. To display the contents of a register, use ATSr? as in this example: ATS20? Register Default Function S0 See DIP Sets the number of rings on which to Switch 5 answer when in Auto Answer Mode. S0=0 disables Auto Answer, the same as DIP switch 5 DOWN (factory setting). S0=1 enables Auto Answer and the modem answers on the first ring. S1 0 Counts and stores the number of rings from an incoming call. S2 43 Stores the ASCII decimal code for the escape code character. Default character is +++. A value of 128-255 disables the escape code. S3 13 Stores the ASCII decimal code for the Carriage Return character. S4 10 Stores the ASCII decimal code for the Line Feed character. S5 8 Stores the ASCII decimal code for the Backspace character. A value of 128-255 disables the Backspace key's delete function. Register Default Function S6 2 Sets the number of seconds the modem waits before dialing. If set to X2, X4, or X6, the modem ignores this register and dials as soon as it detects a dial tone (fast dials). S7 60 Sets the number of seconds the modem waits for a carrier. May be set for much longer duration if, for example, the modem is originating an international connection. S8 2 Sets the duration, in seconds, for the pause (,) option in the Dial command and the pause between command re-executions (> and A> commands). S9 6 Sets the required duration, in tenths of a second, of the remote modem's carrier signal before recognition by the Courier. S10 14 Sets the duration, in tenths of a second, that the modem waits after loss of carrier before hanging up. This guard time allows the modem to distinguish between a line hit, or other disturbance that momentarily breaks the connection, from a true disconnect (hanging up) by the remote modem. While we do not recommend connecting the modem to a line with call waiting, if you have call waiting you may wish to adjust this setting upward to prevent the modem from misinterpreting the signal for a second call as a disconnect by the remote modem. A better alternative is to contact your phone company to find out how to temporarily disable call waiting. S11 70 Sets the duration and spacing, in milliseconds, of dialed Touch-Tones. S12 50 Sets the duration, in fiftieths of a second, of the guard time for the escape code (+++) sequence. Register Default Function S13 0 Bit-mapped register. Select the bit(s) you want on and set S13 to the total of the values in the Value column. For example, ATS13=20 enables bit 2 (value = 4) and bit 4 (value = 16). BitValue Result 0 1 Reset when DTR drops 1 2 Reverse normal Auto Answer operation: on incoming RING, enter Originate Mode and look for Answer tone 2 4 Disable 250 msec. pause before result code display 3 8 On DTR signal, Auto Dial the number stored in NVRAM at position 0 4 16 At power on/reset, Auto Dial number stored in NVRAM at position 0 5 32 Disable HST (used for testing V.32 bis in Dual Standard modems) 6 64 Disable MNP Level 3 (used for testing Level 2) 7 128 Custom applications S14 0 Reserved. Register Default Function S15 0 Bit-mapped register. To set the register, see the instructions for S13. BitValue Result 0 1 Disable the modem's extra high- frequency equalization if it causes problems on shorter-link callsêHST modems only 1 2 Disable online fallback 2 4 Disable 450 bps back channel 3 8 Reset non-ARQ mode Transmit buffer from 1.5K bytes to 128* 4 16 Disable MNP Level 4; retransmitting the larger Level 4 data blocks may be a problem if you expect a great number of errors during a call 5 32 Set backspace key to delete 6 64 Some earlier 2400- bps MNP modems, not made by USRobotics or Microcom, were not fully compatible with the MNP protocol. If you have difficulty making a successful 2400-bps MNP connection with a remote MNP modem, it may be because of this incompati- bility. Set S15 to 64 and try again to make the connection. 7 128 Custom applications only * The default 1.5K byte non-ARQ buffer allows data transfer with X- and Ymodem- type file transfer protocols without using flow control. The 128-byte option allows remote users with slower modems to stop data you're transmitting from scrolling off their screens. When remote users send your computer an XOFF (Ctrl-S) and you stop transmitting, the data in transit from your modem's buffer doesn't exceed the size of their screen. Register Default Function S16 0 Bit-mapped test register. To set the register, see the instructions for S13. For information on testing, see Appendix F. BitValue Result 0 1 Analog Loopback 1 2 Dial test 2 4 Test pattern 3 8 Remote Digital Loopback 4 16 Reserved 5 32 Reserved 6 64 Reserved S17 0 Reserved. S18 0 Test timer for software- initiated loopback testing (&Tn), disabled when S18 is set to 0. See Appendix F. Used to set the duration of testing, in seconds, before the modem automatically times out and terminates the test. S19 0 Sets the duration, in minutes, for the Inactivity Timer. The timer activates when there is no data activity on the phone line and at the timeout the modem hangs up. S19=0 disables the timer. S20 0 Reserved. S21 10 Sets, in 10-millisecond units, the length of Breaks sent from the modem to the DTE. Applies to ARQ mode only. S22 17 Stores the ASCII decimal code for the XON character. S23 19 Stores the ASCII decimal code for the XOFF character. S24 150 Sets the duration, in 20- millisecond units, between pulsed DSR signals when the modem is set to &S2 or &S3. The default is 3 seconds. Register Default Function S25 0 Reserved. S26 1 Sets the duration, in 10- millisecond units, of the delay between RTS and the modem's CTS response in synchronous mode. S27 0 Bit-mapped register. To set the register, see the instructions for S13. BitValue Result 0 1 Enable CCITT V.21 modulation at 300 bps for overseas calls. In V.21 mode, the modem an- swers both Bell 103 and V.21 calls, but only originates V.21 calls. 1 2 Enable unencoded (non-trellis-coded) modulation in V.32 mode; this option is part of the CCITT V.32 recommendation, but is rarely used. 2 4 Disable V.32 modulation; used for testing HST modulation in Dual Standard modems. 3 8 Disable 2100 Hz answer tone to allow two V.42 modems to connect more quickly. 4 16 See below. 5 32 See below. 6 64 Reserved. 7 128 Unusual software incompatibility. Some software may not accept 7200, 12000, 14400 and 16800 bps result codes. This setting disables the codes and displays the 9600 code instead. The call's actual rate can be viewed on the ATI6 screen. continued on following page Register Default Function Error control handshaking options: select the total values of bits 4 and 5. Bit 4Bit 5 Result 0 0 Complete handshaking sequence: V.42 Detection, LAPM error control, MNP. 16 0 Disable MNP. 0 32 Disable V.42 Detection and LAPM. 16 32 Disable Detection phase, if you know that the remote modem does LAPM, but not the Detection phase. S28 8 Sets the duration, in tenths of a second, of the extra 3000/600 Hz answer tones sent during V.32 handshaking. Default = 8 (.8 seconds). This gives V.32 modems additional time to connect in V.32 mode before timing out. If there is difficulty answering older, manually operated V.32 modems, for example, modems that require a button to be pushed in order to dial, try lengthening the duration of the extra tones. Setting S28 to zero eliminates the extra tones, resulting in a faster connect time if, for example, the modem is set to use V.21 modulation (300 bps) or V.23 modulation (1200 bps).Sets the duration, in 1/10ths of a second, of the V.32 handshake. Register Default Function S32 1 Sets the function for the Voice/Data switch. This is not a bit-mapped register. Select the value for the desired function, for example, ATS32=6. Value Result 0 Disabled 1 Voice/data, Originate mode 2 Voice/data, Answer mode 3 Redial last number 4 Dial number stored at position 0 5 Auto Answer on/off toggle 6 Reset the modem 7 Initiate Remote Digital Loopback 8 Busy out phone line toggle S34 0 Bit-mapped register. See instructions for S13. BitValue Result 0 1 Disable V.32 bis. Used for troubleshooting; USRobotics' Technical Support may require that you disable V.32 bis for testing purposes. 1 2 Disable the modem's enhanced, propri- etary V.32 bis modulation. Used for troubleshooting. 2 4 Disable the faster retrains that occur during proprietary V.32 bis modulation. Used for trou- bleshooting. 3 8 Enable V.23. Required for some British connections. 4 16 Change MR LED to DSR 5 32 Enable MI/MIC; see Appendix E-5. 6 64 Reserved 7 128 Reserved Register Default Function S38 0 Sets the duration, in seconds, before a forced hang-up and clearing of the Transmit buffer, when DTR drops during an ARQ call. This is provided to allow time for a remote modem to acknowledge receipt of all transmitted data. Default = 0: the modem immediately hangs up when DTR drops. If the modem receives the ATH command, it ignores S38 and immediately hangs up. ASCII CHART