GSP-1620 Power Management
It is very important to follow the proper procedure for powering the GSP-1620 off, per page 7-18 of the GSP-1620 Integrator’s Reference Manual (IRM). To be specific, the user needs to deassert all DTRs on the board, ensure that the DSRs are deasserted, and then and only then, remove power.
We have determined that the IRM is correct when it states that NVRAM of the board will be corrupted if this procedure is not followed. When the NVRAM is corrupted, the modem will behave in unexpected ways when it powers up. For example, the AT$QCSTATUS command issued from a modem in New England might display:
System Availability YES
Since the modem is in New England, it needs to be on Gateway 4, so that is why Gateway 1 rejected its registration. Subsequent issuances of the AT$QCSTATUS command should therefore show different gateways, indicating that the modem is searching for a gateway where it can get Registration: YES. However, we have seen instances where this is not so, and the modem stays in this “limbo” mode forever, until the modem is powered on/off properly. The customer in this situation reports that he had no signal and no communication when, in fact, if he had simply power-cycled the modem properly, he would have obtained service immediately.
There are other examples of NVRAM problems, where AT$QCSTATUS yields responses like MODE: NO_MODE and also other oddities. It is not productive to list all the possible perturbations of problems which can arise from corrupted NVRAM. It is productive to ensure that your application is controlling the GSP-1620 power-down sequence in the proper way because this will ensure that your data modem will have the highest reliability and the highest performance.
A common problem which integrators face is that their end-users simply want to yank the plug on the device when they are done with their job, and do not understand the importance of going through a graceful shutdown of the modem. One way to get around this problem is to go through a silent resetting of the NVRAM every time the GSP-1620 is powered on. This might take a few seconds longer, but the user does not realize the extra boot time, and just knows that he has to wait till the modem is ready before he can transact his data sessions.
One way of resetting the NVRAM upon power-up is to ground the reset pin (pin 25) of the GSP-1620 while the modem is being initially powered, and then release the reset pin. Using this procedure, the GSP-1620 resets its NVRAM upon every power-up sequence. Another way to reset the NVRAM is to power up the GSP-1620, deassert all DTR signals so that the GSP-1620 shuts down gracefully, and then re-assert one of the DTRs before proceeding with trying to register the modem on the system.