Specifications

Operation Theorem •• 27

4.4 Handshaking

In PCI-7200, it also supports a handshaking digital I/O transfer

mode. That is, after input data is ready, an I_REQ is sent form

external device, and I_ACK will go high to acknowledge the data

already accessed.

I_REQ & I_ACK for Digital Input

1. Digital Input Data is ready

2. An I_REQ signal is generated for digital input operation

3. Digital input data is saved to FIFO

4. An I_ACK signal is generated and sent to outside device

5. If the FIFO is not empty and PCI bus is not occupied, the data

will be transferred to main memory

Latch Digital Input

or Digital Output

Digital Input FIFO

Bus mastering

DMA data Transfer

PC's Main Memory

Digital Input DATA

IN_REQ

IN_ACK