Note
Devices that you might use with the HP 64700 Series Emulator may differ in the number of bits they transfer to represent each ASCII character. Although only 7 bits are required to transmit the ASCII character set, many manufacturers of data terminals, host computers, and printers use the eighth bit to extend the ASCII character set with another 128 characters. It is important for the HP 64700 Series Emulator to send and receive characters with the proper number of bits so that characters are represented correctly.
Some examples of differing character sets include:
1. Most UNIX systems send and receive 7 -bit characters.
These include systems such as HP-UX running on HP 9000 Series 300/400 Workstations. However, some applications in an HP-UX workstation may use 8-bit characters to represent certain foreign language characters.
2. Personal computers running the MS-DOS operating system have standardized on the IBM PC-8 character set.
This is an 8-bit character set.
3. Hewlett-Packard printers are standardized on an 8-bit character set known as Roman -8.
4. Most all other systems will use only the standard 7 -bit ASCII character set.
If you intend to use a binary transfer protocol (such as the HP 64000 transfer utility) to transfer programs or trace listings between a host computer and the HP 64700 Series Emulator (or another device connected to the other HP 64700 Series port), you must set the HP 64700 Series Emulator to send and receive 8 bits.
Refer to the manuals for the other devices used with your system (data terminals, host computers, printers, etc.) to determine the correct number of bits used by the device. Remember that you should set all devices to the same number of bits per character; for example, if your host computer uses 8 bits per character, and you are using the HP 64700 Series Emulator in the Transparent Configuration, you should set the HP 64700 Series Emulator and the data terminal to 8 bits per character.
Once you have determined the correct number of bits per character, set the HP 64700 Series Emulator rear panel
configuration switch to the correct value. See figure 5-19 for the switch settings.
If you want the HP 64700 Series Emulator to send and receive 7 bits per character, set switch S9 to a one (1).
If you want the HP 64700 Series Emulator to send and receive 8 bits per character, set switch S9 to a zero (0).
8 BIT
CHARACTERS
7 BIT
CHARACTERS
Figure 5·19. Character Length Configuration Switch
System Configuration 5·33
Setting Local Echo
When you type characters on a keyboard, some software must to send the characters received to your display screen so that you can monitor what you have typed. This is known as "echoing" the characters. Each system handles echo in different ways. For example, in most Hewlett-Packard computer systems, the host computer automatically echoes characters typed in at a data terminal. Even though HP data terminals provide an echofunction, the correct configuration at the data terminal is to disable the local echo. Otherwise, every character typed at the keyboard would appear twice on the display screen.
Each HP 64700 Series Emulator provides a configuration switch to enable or disable the echo function. If enabled, each character received by the HP 64700 Series Emulator is echoed back on the same port as received. If disabled, the characters received are not echoed back. With Hewlett-Packard computers, you will normally want to enable the local echo function. See figure 2-20.
Normally, you want the active device furthest from your input echoing back characters. This provides you with feedback that the receiving system is receiving characters. For example, in
Stand-alone Configuration, you would want to enable the HP 64700 Series Emulator echo function and disable the data terminal's echo function. Then, if anything goes wrong with the data communication cable or with the HP 64700 Series Emulator, you will be immediately aware of a problem since character echo will cease. Conversely, if you enabled the data terminal echo function and disabled it on an HP 64700 Series Emulator, you might not be aware of such a failure. (Although the HP 64700 Series Emulator would cease sending command prompts or requested information to the data terminal, anything you typed in would echo.)
Refer to manuals for your other devices to determine a need for echo. A good way to determine echo requirements is to draw out your configuration and show which devices automatically echo characters as part of their system software and cannot disable echo.
Then look at other devices in the chain and determine whether they will need to echo characters back to other devices.
Once you've determined the need for echo, set the rear panel configuration switches on the HP 64700 Series Emulator. See
CHARACTER S E N T '
-HP 9000 SERIES 300 COMPUTER
DATA TERMINAL RUNNING HP-UX (ECHO ALWAYS)
W I LOCAL ECHO DISABLED
PORT B PORT A CHARACTER SENT
---CHARACTER ECHOED
r---, r---,
DATA TERMINAL W/LOCAL ECHO DISABLED CHARACTER S E N T
-DATA TERMINAL W/LOCAL ECHO DISABLED
HP 64700 EMULATOR IN TRANSPARENT MODE (NO ECHO OCCURS
EVEN IF ENABLED) HP 9000 SERIES 300 COMPUTER RUNNING HP-UX (ECHO ALWAYS)
Figure 5·20. Echoed Characters In Your System
System Configuration 5·35
ECHO ENABLED
1. To have the HP 64700 Series Emulator echo characters received (on either port), set switch S8 to zero(O).
2. If you don't want the HP 64700 Series Emulator to echo characters received, set switch S8 to one (1).
ECHO DISABLED
Figure 5·21. Echo Enable/Disable Configuration Switch