Data modem
An improved data modem (IDM) and method includes a communication processor module, a mass storage module, a power converter module, and one or more DSP modules. The communication processor module utilizes commercial off-the-shelf components as well as electrically programmable logic devices (EPLD), which are programmed to provide a watchdog timer, programmable interrupt controller, flash page addressing, ISA bus decoder and controller, and various circuits and logic.
1. A data modem having an Input Output Module (IOM), wherein the IOM comprising:
a digital portion and an analog portion;
the digital portion comprises:
a digital signal processor (DSP);
a SDRAM bank connected to the DSP via an External Memory Interface (EMIF) bus;
a DSP-interface Field Programmable Logic Device (FPLD) interfaced to the DSP via the EMIF bus;
a watchdog implemented in a field programmable logic device;
a low-side driver interfaced to the DSP-interfaced FPLD, the DSP-interfaced FPLD including a multiplexer, controlled by a system reset, allowing signals to be routed to the low-side driver before the DSP-interface FPLD is loaded with operational code; and
Low Voltage Differential Signaling (LVDS) drivers/receivers.
2. The claim 1 , wherein the analog portion comprises:
an Analog-Interface Field Programmable Logic Device (FPLD) connected to the LVDS drivers/receivers;
CODECS and analog circuitry connected to the analog-Interface FPLD;
ASK/FSK radio input/output circuits coupled to the CODECS and analog circuitry; and
radio control and status inputs/outputs coupled to the Analog-Interface FPLD.
3. The IOM of claim 1 , wherein the watchdog comprises a counter and an associated software-accessible register, and wherein the watchdog is initialized by a software and operates under hardware control.
4. The IOM of claim 3 , wherein the software-accessible register is accessed by periodically the software so as to reset the counter and to prevent the counter from reaching a terminal count during normal operation, and wherein the IOM is reset if the terminal count is reached.
5. The IOM of claim 1 , wherein power is removed from the DSP and the SDRAM during a reset so as to force the SDRAM to reset and to allow the interface between the DSP and the SDRAM to operate properly.
6. The IOM of claim 1 , wherein, using the multiplexer, the low-side driver is initialized before the DSP-interfaced FPLD is loaded with operational code.
7. The IOM of claim 2 , further comprises a master clock connected to the CODECS, wherein a sampling phase of the CODECS is adjustable by increasing or decreasing the frequency of the master clock thereby effecting a shift in the sampling phase.