tap

This page is included for those who want to develop their own paging control software or add an interface for the WaveWare Paging Encoder to their existing software applications.

A simple definition of the TAP protocol is that the TAP protocol normally requires a connect and disconnect process and normally assumes that the Host system maintains a database of pager reference numbers called IDs, and that the paging system maintains a database of all paging parameters associated with each ID. The TAP interface supports paging messages up to 244 characters in length. The actual maximum length of transmitted messages in the WaveWare TAP interface is 245 minus the ID field length. With an ID value of 5, you can transmit up to 245 characters per message. With an ID value of 1233425120, you can transmit up to 235 characters per message.

To configure your WaveWare Paging Encoder to use the TAP paging protocol, you may be required to configure the DIP switch bank in the paging encoder. Please refer to Appendix B – Com Port Settings, for details on configuring communication protocols, in the WaveWare SPS-5 v8 Manual.

Your WaveWare Paging System typically communicates with a PC or other host device via RS-232 at 9600 Baud, 8 data bits and 1 stop bit. The eighth data bit is ignored (no parity). You can configure the paging system for other serial communication parameters. Please refer to Appendix D – DIP Switch Settings, for details on serial communication parameters, in the WaveWare SPS-5 v8 Manual.

The paging encoder maintains an input buffer which can receive commands from the PC while a page is being transmitted. The input buffer should be able to contain approximately ten paging messages before getting full. When a command is received from the PC, the paging system responds with a message that includes error messages if the command was not understood or not properly transmitted. The first three digits of each paging system response conforms to the response codes defined in the TAP v1.8 specification. See Appendix F – TAP Response Codes for a listing of the response codes, in the WaveWare SPS-5 v8 Manual.

The paging encoder encodes paging messages into POCSAG paging format and transmits the encoded paging message. If the Carrier Detect function is enabled, transmissions will be delayed while interfering signals are detected.

The TAP mode of operation can be supplemented with two additional functions, including Host Monitoring Function, and Contact Monitoring Function. See Appendix L - Host Monitoring Function and Appendix M - Contact Monitoring Function, for operational details, in the WaveWare SPS-5 v8Manual.

The operational modes available for paging using the TAP Paging Protocol include:

• System Identification Command

• Paging Session Login

• Paging Operation

• Paging Session Logout

The System Identification command allows installation programs and other software applications to poll serial ports for the existence of a WaveWare paging encoder using the standard ATI command. This can be used for a supervised process (also called keep-alive) where the host system periodically polls the paging system for a response. When the WaveWare paging transmitter recognizes a command formatted as ATI<CR> , the transmitter responds with the following message:

The Host Device initiates the Login process by transmitting a carriage return character <CR> every two seconds until the paging system properly responds or until the Host Device times out and notifies the operator of a bad connection. The paging system will respond with “ID=<CR> ” (Note: the quotation characters are used here only for reference and are not included in the transactions). The “ID=<CR> ” will not be repeated or timed out by the paging system.

The “110 1.8” message indicates that the system conforms to TAP specification version 1.8 and should be backward compatible with earlier TAP implementations. The paging system then notifies the Host Device that it is ready to accept messages as follows:

The Paging Session Login mode allows a Host Device, sometimes called a Remote Entry Device, to initiate communications with the paging system. With the WaveWare Paging System, the Login process is optional. The WaveWare Paging System will automatically login a Host Device and process the paging message if it recognizes a properly formatted TAP message block at any point in it's operation.

Paging transactions are transmitted in blocks of characters, where one transaction is sent per block. Each block sent by the Host Device is acknowledged by the paging system. The Host Device must wait for this acknowledgement before sending the next block.
The WaveWare Paging System provides acknowledgement in the form of an <ACK> character.

The WaveWare Paging System supports TAP message blocks up to 253 characters in length, with a 235 to 244 character message, from 1 to 10 characters for ID (pager number), plus 5 control characters, and a 3 character checksum. (Message field length is restricted as follows: when a 1 character ID is used, a 244 character message can be accommodated, and so on, for a total of 253 characters, such that when a 4 character ID is used, a 241 character message can be accommodated. The maximum ID field length of 10 causes a maximum message field length of 235 characters). A block always carries two fields with their associated carriage returns. The message field may be empty, but it's carriage return must be included in the data block. The TAP message block format is as follows:

The ID field is a one to ten character pager number. Leading zeroes are not required. The Message field accommodates up to 235 alphanumeric characters. The Checksum field provides a checksum for the previous portion of the TAP message block. See Appendix D - TAP Checksum Calculation, for sample code to create the checksum field, in the WaveWare SPS-5 v8 Manual.

Control characters can be embedded into paging messages so that high end alpha pagers and paging data receivers can respond with formatted screen displays and with formatted serial output, as required. Control characters (typically and) can be embedded in messages by using the Transparency Option.

The Transparency Option replaces a non-printable control character with the SUB (Hex 1A) character immediately followed by the control code offset by 40 Hex. See the Appendix G-Embedded Control Characters for details on how to embed control characters in paging messages, in the WaveWare SPS-5 v7 Manual.

Method 1 - ID field lengths from 1-4 digits will cause a pager database lookup. ID fields of this format must contain numeric digits only. The numeric ID value will be compared to the ID values stored in the WaveWare Paging Systems's onboard pager database.

Method 2 - ID field lengths from 5-10 digits will cause Extended ID processing. Extended ID processing assumes that the last 3 digits of the ID field define paging message encoding attributes, while the preceding digits define the pager cap code. Extended ID processing allows you to avoid the process of confinguring a pager database in the WaveWare Paging System. See Appendix E - Extended ID Processing for details on how to format the ID field, in the WaveWare SPS-5 v7 Manual.

When the Host Device delivers a TAP Message Block to the WaveWare Paging System, if the message block is properly formatted, and a 1 to 4 digit ID field matches the pager database, the paging system will respond with an initial response code as follows:

If your WaveWare Paging System is configured to operate using TAP Non-Verbose mode, the paging system will respond only with an initial response code of:

Following the first part of the TAP message block response, if the input buffer of the paging system has capacity for another TAP message block, the paging system will send the following message.

The <ACK><CR> response can be used as a flow control method to prevent overflow and lost messages. As alternative flow control methods, you can use either hardware or software flow control. If the paging system DIP switch is set to hardware flow control mode, the RS-232 CTS signal will be deasserted when the input buffer doesn't have capacity for another TAP message block, and reasserted when capacity exists in the input buffer. If the DIP switch is set to software flow control mode, an XOFF character (0x11) will be output in the response string to indicate the input buffer doesn't have capacity for another TAP message block. When capacity is available, an XON character (0x13) will be output.

When the Host Device delivers a TAP Message Block and a checksum error occurs, the paging system will respond with an error message and a <NAK><CR> , which tells the Host Device to resend the transaction. See Appendix E - TAP Response Codes for more information on paging system response messages, in the WaveWare SPS-5 v8 Manual. If the TAP Message Block checksum is OK, but the Message Block violates formatting rules, the paging system will respond with an error message and an <RS><CR> , which tells the Host Device to abandon the transaction. An example error message sequence follows:

The Paging Session Logout mode allows a Host Device, sometimes called a Remote Entry Device, to stop communications with the paging system. With the WaveWare Paging System, the Logout process is optional. The WaveWare Paging System will automatically login a Host Device and process the paging message if it recognizes a properly formatted TAP message block at any point in it's operation.