CHAPTER 9: DIP-Switch Settings

Switch #12

Asynchronous/Synchronous Operation -- "Sync"

(Asynchronous/Synchronous Mode/Leased Line/Dial-Up)

The Series II Modem can operate in either Asynchronous mode or Synchronous mode. In Synchronous mode, start and stop bits are eliminated. The modem's internal clock circuits on the RS-232C/V.24 pins 15 and 17 are activated. The Series II Modem's Command mode is not accessible in Synchronous mode. This switch is a means to alternate and to access either mode. In Synchronous mode, you may want to set the RTS forcing and CTS forcing DIP-Switches so that both of signals act normally (not forced on).

Synchronous Operation

=

Switch #12 UP

Asynchronous Operation

=

Switch #12 DOWN

Factory Default Setting

=

DOWN

Switches #13 and #14

Speed Switches

(Synchronous Mode/Leased Line)

DIP-Switches #13 and #14 are used to set the Series II Modem’s data transmission rate. Switches #13 and #14 are used in combination, typically in leased-line and call origination applications. Note that the modem baud rate command ($MB33600) overrides the setting of these speed selection switches (DIP switches #13 and #14).

28800 bps Operation

= Switch #13 UP and Switch #14 UP

19200 bps Operation

= Switch #13 DN and Switch #14 UP

14400 bps Operation

= Switch #13 UP and Switch #14 DN

9600 bps Operation

=

Switch #13 DN and Switch #14 DN

Factory Default Setting

=

Switch #13 UP and Switch #14 UP

Switch #15

Carrier Detect/DSR Forcing -- "DSR"

(Asynchronous/Synchronous Mode/Dial-Up/Leased Line)

Some terminals react in unusual ways to the toggling of the Carrier Detect (CD - RS-232C/V.24 pin 6) signals. The most common symptom is that the modem does not respond to commands, or does not echo characters. In these cases, it is advisable to force these two signals On in order for the terminal to communicate properly with the modem in

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