Si2493/57/34/15/04
Global ISOmodem-EVB
4 Rev. 0.7
1.3.1.1. RS232 vs USB vs User Provided IO
Selection
To change to USB operation simply move the RS232
selection jumper on JP23 to the USB position as
marked on the PCB and shown in Figure 1. When the
USB vs UART settings are changed the appropriate
indicator LED will light up on the EVB.
If neither jumper is in place then neither serial port will
be activated and the user must provide I/O signals via
the pins on J103. This IO can be in ASYNCH SERIAL,
SPI SERIAL and Parallel Bus mode.
1.3.1.2. Autobaud Control
Autobaud is enabled with no jumper at the JP34
position. When a jumper is in place, autobaud is
disabled and the user must setup the host to run 19k2
baud in order to use the modem.
1.3.1.3. EEPROM Control
To enable the EEPROM (U5) both jumpers JP34 and
JP35 must be in place and the modem reset.
JP35 physically connects the EEPROM chips select
line to the modem and allows the EEPROM to function
when addressed by the modem, while JP34 connects a
strapping option to the correct modem pin which is
sensed during reset and instructs the modem firmware
to use the EEPROM.
1.3.1.4. Call Progress Configuration
The modem call establishment can be heard by
enabling the call progress feature via software (see
AN93) and Hardware. The hardware components
include installing JP12 which enabled the audio power
amplifier and installing JP14 to connect the on board
speaker to the power amplifier output. If an offboard
speaker is to be used then JP14 can be removed and
the alternate speaker can be connected to pins 1 and 4
of JP11. Note the this audio output is 8 and
differential so that neither output pin should be
grounded.
1.3.1.5. Control Line Configuration
Various modem control lines can be rearranged
depending on the user preferences and the specific
modem chips used. This is done using JP6. The basic
two JP6 configurations are shown in the following
figures.
Figure 2. Default J6 Setup for 24-Pin Modem
Chips
Figure 3. Default J6 Setup for 16-Pin Modem
Chips
The specific details of what the jumpers connect are
shown in Table 1, which is also found printed on the
underside of the EVB.
Table 1. Routing of Control Signals with Jumper Position on J6
RS232
Signal
Si24xx 24-Pin Si24xx 16-Pin Si2401
Left Right Left Right Left Right
DCD DCD SDI/EESD DCD NC DCD
NC
RI RI FSYNCH
NC RI NC RI
DTR ESC RI ESC
NC ESC NC
RTS RTS SDO/
EECLK
NC RTS NC GPIO1
DSR INT AOUT/INT
NC INT NC AOUT/INT
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