I have GPRS modem MD720-3 and PLC 224. I can’t run standard demo project “SET 21” PPI cable work (all leds show that), but in standard block WDC_INIT modem answer error (I think so). Modem is waiting PIN code all the time. I try without PIN (removed PIN from phone) then modem S led is OFF (GPRS is not able). Where can be a problem?

In the beginning i had a similar problem and i realise that the problem was in haven't PIN so i set a PIN in the SIM with a celular phone and after that it worked....

you can also try to use Hyper Terminal and test AT commands to see if the modem is responding correctly... the AT command for release the PIN is AT+CPIN=<value>.

Hope this help..........

I think my modem is broken. I can input any PIN and modem answer will be OK. I removed SIM from modem and response is the same.

Command: AT+CPIN=?
Response: OK
Command: ATTTTTTTTTTTT
Response: OK

I removed SIM card from modem but modem answer the same.
I can input all commands with “A....” and answer will be OK. I try to load default and result is the same.

Is my modem broken?