CHAPTER 6. PHONE INTERFACE

6.5 VIRTUAL ETHERNET

C. Data service pin control

Equipment called DPRAM is used for communication between PDA and PHONE. DPRAM-Dual Port RAM- has 2 ports and 2 regions for input. One region is assigned to PDA and the other is to PHONE. And each region is divided into Formatted Area and Unformatted Area.

a. Pin control flow

To use data communication, Unformatted Area of DPRAM should be activated. Through the activated area, the source data of network is interchanged and PPP demon interchanges the data with network application. The following is scenario for PIN control.

-> PDA requests DTR assert
-> PHONE responses DSR assert
-> PHONE checks status of electric field
-> According to the status of electric field, response DCD assert or not
-> PDA executes AT Command
-> PDA tries to send call through CHAT
-> If the call connected, RF of PHONE is opened
-> Authenticate with base station for PPP service and negotiate IP
-> IP arrangement