Asynchronous Emulation

In Asynchronous Emulation the HSM is viewed by the Host as a DCE (data communications equipment) device, and does not require a modem. The electrical interface between the Host and the HSM can be configured to conform to the RS-232 or X.21 standard.

To configure the HSM for asynchronous communications:

· The port must be defined as a DCE.

· Details held in software must be configured.

The following variables can be configured:

· The required length of the message header. This is normally set to 4, but can be set between 1 and 255. This depends on the value used by the Host computer application.

· The baud rate of the Host computer port.

· The word format of the Host computer port.

· The required communications protocol, either standard or transparent asynchronous ASCII.

· The asynchronous terminating characters. The terminating sequence can be either one or two characters. To select the terminating characters four hexadecimal values must be entered. If only one terminating character is required, enter the first two hexadecimal values followed by 00.

Message Header Length

Each transaction to the HSM begins with a string of characters (header) which the Host can use to identify the transaction (or for any other purpose). The HSM returns the string unchanged to the Host in the response message. The length of the header can be set to any value between 1 and 255; the default value is 4.

Transparent Asynchronous Communications

In the standard asynchronous mode of communication, codes like STX (X’02) and ETX (X’03) have a special meaning, but they can sometimes occur in a stream of binary data, where that special meaning does not apply.

To avoid ambiguity, Transparent Asynchronous Communications mode is used. This has a simplified message format (for details see the Programmers Manual).

The Host port of the HSM must be configured for Transparent Async Communications and 8-bit data transfers.

Standard Asynchronous Communications

In the example, standard asynchronous communications is enabled, the message header length is 4 characters and the terminating characters are set to 0300 hexadecimal (ETX). The Host baud is changed from 300 to 19200 bps; the word format to 8 data bits, no parity and 1 stop bit.

Example:

Offline> CH <Return>

Message header length (1-255): 4

Asynch, Ethernet, or SNA-SDLC 3274 [A/E/S]: A

Transparent mode (Y/N): N

Terminating characters (4 hex): 0300

Interface: DTE or DCE [T/C]: C

BAUD RATES		WORD FORMATS
1.	300	1.	7 bits, no parity, 1 stop
2.	600	2.	7 bits, odd parity, 1 stop
3.	1200	3.	7 bits, even parity, 1 stop
4.	2400	4.	8 bits, no parity, 1 stop
5.	4800	5.	8 bits, odd parity, 1 stop
6.	9600	6.	8 bits, even parity, 1 stop
7.	19200
8.	38400

In response to the prompts, enter the number of the

desired option or <RETURN> for no change.

Host baud rate: (current value = 1) 7 <Return>

Host word format: (current value = 2) 4 <Return>

Save HOST settings to smart card? [Y/N]: N <Return>

After completing the procedure reset the HSM by pressing the RESET button on the front panel. The new values do not take effect until this has been done.

Transparent Asynchronous Communications

In the example, transparent asynchronous communications is enabled and the message header length is set to 6 characters.

The Host baud is changed to 9600 bps and the word format is set to 8 data bits, no parity and 1 stop bit. No option of message terminating characters is offered because this is fixed (value X'03, "ETX" character).