User’s Manual
GSM35
12
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Base address jumpers (Factory setting: 2E8h / 6E8h)
The GSM35 is I/O mapped into the memory space of your host XT/AT.
The board occupies a consecutive memory window of 8 bytes starting
from the base address for UART communication and 4 consecutive bytes
starting from BASE+400h for the board control and status registers. As an
example if your base address is set to be 2E8h for the serial port, the
onboard control registers will start from 6E8h.
The most common cause of failure when you are first setting up your
module is address contention: some of your computers I/O space is
already occupied by other devices and memory resident programs. When
the GSM35 attempts to use it's own reserved memory addresses (which
are being already used by another peripheral device) erratic performance
can occur and the data read from the board may be corrupted.
To avoid this problem make sure you set up the base address by using
the six jumpers on the right side of the board, this allows you to choose
from a number of different addresses in your host computer’s I/O map.
Should the factory-installed settings be incompatible to your system
configuration, you may change this setting to another using the options
illustrated in Table 2-2 (overleaf). The table shows the jumper settings
and their corresponding values in hexadecimal form. Ensure that you
verify the correct location of the base address jumpers. When the jumper
is removed it corresponds to a logical "0", connecting the jumper to a "1".
When you set the base address of the module, record the setting inside
the back cover of this manual.
