Bus Communication
Each card has a jumper selectable number, which forms the address for the card. To start with, all cards are in listening mode just after initialization, which means that data is directed into the cards. The data bus is 16 bits wide and ddir, iodclk, hshkout, hshkin, ioclkdir are the associated control signals. Proposed scheme for communication as mentioned. The data transfer is in form of 16-bit word and is in handshake mode. The PC initiates all communications. Out of 16 bits meant for transfer lower 8 bits dio [ 0..7 ] are address of card for whom the word is intended and dio[ 8..15 ] are the data. Rest of the data transfer is in form of packet communication as is been described in FFT control and related issues. The communications intended for PC are also in same format as for the cards.
Description of sample data transfer is as follows:
PC initiates the communication by placing a valid address and data on 16-bit bus. Then it pulls down the handshake out ( hshkout ) signal ( which is handshake in for the card ). All the cards on bus senses the low on hshkin and then matches the address with there own and if the decoded address is same as the card address the data byte is interpreted by the card and appropriate action taken. Then card lowers the hshkout signal in response, which signals the proper end of transfer. The data bus is then, released by the host communicator for other transfers. Rest of cards ignores the data.
Image Gallary GOBACK TO Delay-DPC SUBSYSTEM
GOTO DIGITAL BACKEND