Volt Digital) and Vd+3.3 (3.3V Digital) are created and made available to the I/O Modules via the
Interconnect Port. The DSP Core voltage, Vd+1.2 is also created via a switching power supply.
The dspstak 21262sx DSP Engine does not use Va+, Va+5 or Va-. These supplies are available to
I/O Modules. If the I/O Module does not need a negative supply, you can power the dspstak
21262sx with only a positive DC power supply. The recommended input voltages are 9 VAC or 9 to
15VDC. Since switching regulators are used for the digital supplies, the input voltage is not critical.
In all cases, the DC supply or an unregulated DC supply created from an incoming AC supply
should be less than 20VDC. This will protect both the DSP Engine and probably the components on
the I/O Module.
One final thing to remember: The nominal output voltage of a wall adapter is usually much lower
than its actual output voltage. We recommend that unregulated DC wall adapters should have an
maximum nominal voltage of 12VDC.
RS-232 Interface
The RS-232 interface is used to upload user application programs and to program the clock
generator in the command mode. An application program may also use the RS-232 interface for its
own purposes. The RS-232 port is provided by a dedicated microcontroller that also has other
functions on the dspstak 21262sx. These functions are all available via the SPI port of the DSP. The
API for these functions is described in the Software Section of this manual. There are also software
examples on calling these functions on the CD.
The RS-232 interface is configured as a DCE (Data Communications Equipment) device. It uses a
DB-9F connector that is designed to mate without crossover connections to the DB-9M connector
found on PC compatible computers. Connections are defined in the following table:
Signal Direction Pin
Notes
DCD
1
DCD, DTR & DSR are connected together
RD
DCE -> DTE
2
TD
DTE -> DCE
3
DTR
4
DCD, DTR & DSR are connected together
SIGNAL GND
5
DSR
6
DCD, DTR & DSR are connected together
RTS
DTE -> DCE
7
Not currently supported
CTS
DCE -> DTE
8
Not currently supported
RI
9
NC
dspstak™ 21262sx User Manual
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