DSP9612RM USER’S GUIDE
0049-0519-000
Page 15
REV.D
SW3-1
−
Fast Poll Auto Rate/FSK
SW3-1
ON = Low-Speed Mode (FSK)
OFF = High-Speed Mode (Fast Poll)
The modem has two operating modes:
FSK mode, which supports data rates from 0 to 1800 bps.
Fast-poll mode, which supports data rates of 4800 and 9600 bps.
SW3-1, along with the Data Rate Selector (DRS) pin on the modem’s RS-232
connector, configures the modem for either FSK or fast-poll mode. Table 2-6
shows how SW3-1 and the DRS signal configure the modem for these operating
modes.
Table 2-6. Modem Operating Mode
To Select…
Set SW3-1 to…
And the DRS Signal…
Fast-poll mode
OFF
Is not connected or is set
HIGH
FSK mode
OFF
Is set LOW
FSK mode
ON
Doesn’t care
You should use the DRS signal in RTS control mode. It does not work in either
constant carrier mode (SW3-8 set to ON) or in the auto-RTS mode (SW3-4 set to
ON). The DRS signal is only sampled when the transmitter is idle (when not
sending a preamble, data, or a turn-off sequence).
Note that the DRS control both the transmitter and receiver. If DRS changes
states while the modem is receiving a preamble, data, or a turn-off sequence, the
state of the receiver is unknown until the carrier drops and a new preamble is
received. We recommend that the DRS does not change states until both the local
and remote modems’ transmitters are in the idle state. When they are, both the
local and remote modems’ DRS signal should change states.
SW3-2
−
Data Rate (Fast-Poll Mode Only)
SW3-2
ON = 4800 bps
OFF = 9600 bps
SW3-2 configures the modem speed. When the modem is in high-speed fast-poll
mode (SW3-1 OFF), setting SW3-2 ON selects 4800 bps, while setting SW3-2
OFF selects 9600 bps.
