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Remote Operation via RS-232 Interface
Baud Rate
Four different baud rates are available. These are selected by changing rear panel switches
numbers three and four as shown in table 2-6. When a switch is changed the new baud rate
IS displayed on the front panel.
Table 2-6. Baud Rate Selection: switches 3 and 4
Baud Rate
Switch 3
Switch 4
I
300
'
1200
up
up
up
down
2400
down
up
4800
down
down
Word Length and Parity
Word length and parity are selected by setting switches five and six as shown in table 2-7.
Table 2-7. Switch settings for word length and parity: switches 5 and 6
Description
Switch 5
Switch 6
7 data bits, 1 parity bit, even parity
up
UD
7 data bits, 1 parity bit, odd parity
up
down
8 data bits, no parity
down
up
7 data bits, 1 parity bit, parity bit always 0 (zero)
down
down
Handshake Selection
Handshaking, or receive pacing, is performed by the HP 3325B to prevent its character
buffer from overflowing. Data is lost if it is sent to the HP 3325B when its data buffer is full.
buffer can hold 256 characters. The handshaking may be accomplished with one of
^0
different methods, selected with switch 7: software handshake or the hardware
handshake.
^_^^software handshaking is selected, the HP 3325B sends the Xoff character (decimal 19
IS room for less than 128 characters in its buffer. After sending Xoff the
1^ oo25B processes characters until there is room for 256 characters, when it sends the Xon
character (decimal 17 or DCl) to indicate that it is ready for more characters.
The hardware handshake performs the same function using hardware connections to signal
its readiness for data. Both the RTS (request to send) and DTR (data terminal ready) lines
^come false (-10V) when there is room for less than 128 characters in the character buffer.
Ihis handshake is not recommended when the HP 3325B is connected to a modem since
dropping the DTR line may cause the modem to disconnect.
'^e HP 3325B uses receive handshaking, only. It does not respond when it receives the Xoff
hardware connection is made which would signal it to stop sending data.
^1 data sequences sent by the HP 3325B are short enough that transmit pacing should not
be necessary.
®
2-14
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