DSP9612RM USER’S GUIDE
0049-0519-000
Page 16
REV.D
SW3-3
−
Async Character (Fast-Poll Mode Only)
SW3-3
ON = 11 bits
OFF = 10 bits
Switch SW3-3 selects whether the async character is 10 or 11 bits long. When the
modem is in high-speed fast-poll mode (SW3-1 OFF), setting SW3-3 ON selects an 11-
bit async character, while setting SW3-3 OFF selects a 10-bit async character.
SW3-4
−
Auto RTS (Fast-Poll Mode Only)
SW3-4
ON = Enable Auto RTS
OFF = Disable Auto RTS
For data terminals that do not support hardware RTS, set SW3-4 to ON to enable auto
RTS mode. In this mode, TXD is detected at the modem and an internal RTS signal is
turned ON. After training completes, the TXD is transmitted to the remote modem. The
transmitter turns off if no TXD is detected after 1 character length of idle time. Auto RTS
is used in fast-poll mode only (SW3-1 set to OFF).
SW3-5
−
Transmitter Termination
SW3-5
ON = Switched by RTS
OFF = 600
Ω
SW3-5 is used for multi-point configuration networks. When multiple modems are
connected on the same metallic circuit:
The transmitter termination should be of high impedance if the modem is not
transmitting.
The transmitter is only terminated with 600 ohms when RTS is asserted.
This configuration should be used for all slave modems to prevent the transmitting
modem from being unnecessarily burdened. To select this configuration, set SW3-5 ON
on the slave modems.
If you use the modem with transmission lines that are transformer-coupled or with an
impedance-isolated network (such as a transformer bridge), set SW3-5 to OFF for proper
operation.
SW3-6
−
Reserved (Test Only)
SW3-6
Must be OFF
SW3-6 must be in the OFF position for normal operation.
