The SNA-SDLC interface in the HSM emulates a 3274 Control Unit (CU) with a single device attached. At the SNA level, this control unit appears as two Network Addressable Units (NAU); a Physical Unit (PU) and a Logical Unit (LU). A standard 3274 CU contains 32 such LUs.
NOTE: IBM SRM users please refer to the relevant manual.
The electrical interface between the Host and the HSM conforms to the RS-232-C standard.
The following are configurable options available in the SNA-SDLC environment:
· The message header length (1 to 100 characters).
· The character set can be selected as EBCDIC or ASCII.
· A "Transparent" Data mode can be selected.
· The HSM can support the IBM IMS and CICS environments.
· The Host interface can be through either the DCE or DTE port.
· The Host interface can use the RS-232-C.
· The baud rate can be selected (if DCE).
· The SDLC Station Address.
When the SNA-SDLC mode is selected, the standard HSM command/response message, as defined in the Programming Manual, is invalid. In an SDLC environment, the use of the start and end of text characters, STX and ETX, is not relevant, and they are omitted from all messages. Messages therefore start with the Message Header and end with either the last data element or the Message Trailer if it is present.
Each transaction to the HSM begins with a string of characters 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 100; the default value is 4.
If the "Normal" (default) setting is selected, the HSM scans each incoming message for any 3270 "Orders". When such an Order is found it is removed from the message and the HSM proceeds to process the message as normal.
If the "Transparent" setting is selected, 3270 Order removal is not carried out, and it is the responsibility of the Host system to ensure that 3270 Orders do not appear in the data sent to the HSM. Hence, in transparent data mode, the messages sent to the HSM can contain binary data.
The character set can be selected as either EBCDIC or ASCII.
The HSM can be made compatible with an IBM Host running applications under IMS or CICS.
In IMS applications, the HSM requires the entry of one or more test strings to enable it to distinguish between valid transactions and system error and status messages. When the Host software is written, the programmer must insert one of the test strings in the message header field of each valid transaction to the HSM.
The HSM searches for the strings and accepts a transaction only if it contains one of them. It allows a maximum of 20 characters (including delimiters) to be entered. The strings, delimited by commas, can contain any alphanumeric character, and do not need to be the same length. If more than one string is defined, the HSM accepts a transaction if it matches any one of them.
In addition, a test string offset is required. This value allows the test string to be placed at any fixed position in the message header, by specifying the number of characters to skip before the comparison is made. It can be any value from zero to the message header length (but if the header length minus the offset is less than the length of a test string, that particular string will never be found).
All messages that do not have one of the test strings at the defined offset are ignored, and the HSM responds with a PA2 AID at the next poll.
In CICS applications, the HSM searches the beginning of each transaction for the DFH string, which identifies all CICS system messages. If it is found, the message is ignored and the HSM responds with the CLEAR AID at the next poll.
The station address is the address of the secondary station (in this case the HSM). This address must be the same as defined in the Host system configuration. The default address is X'C1.
The baud rate is configurable only when the DCE option is selected. The word format is preset to: no parity, 8 data bits, one stop bit, when SNA-SDLC mode is selected.
For DCE or DTE operation, the configuration is set up using the CH (Configure Host) command during the software configuration process.
Example : (No IMS or CICS, DCE, RS-232-C Interface)
In this example, neither IMS nor CICS support is selected. The RS232 interface is fitted. The HSM is a configured as a DCE (Data Communications Equipment), i.e. the HSM supplies the Clock signal for the RS-232-C interface. The Host baud is changed to 19200 bps.
Offline> CH <Return>
Message header length (1-100): 4
Asynch, Ethernet, or SNA-SDLC 3274 [A/E/S]: S
EBCDIC/ASCII [E/A]: E
Transparent Mode (Y/N): N
Station Address (2 hex): C1
IMS/CICS/General (I/C/G): G
DTE/DCE (T/C): C
RS232 (R): R
BAUD RATES
1. 9600
2. 19200
3. 38400
4. 56000
5. 64000
In response to the prompts, enter the number of the
desired option or <RETURN> for no change.
Host baud rate: (current value = 1) 2 <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.