Visible to Intel only — GUID: iga1405555111850
Ixiasoft
Visible to Intel only — GUID: iga1405555111850
Ixiasoft
5.2.4.2. Agent Mode Operation
In agent mode, the SPI ports behave as shown in the table below.
Name | Direction | Description |
---|---|---|
mosi | input | Data input from the host |
miso | output | Data output to the host |
sclk | input | Synchronization clock |
ss_n | input | Select signal |
In agent mode, the SPI core simply waits for the host to initiate transactions. Before a transaction begins, the agent logic continuously polls the ss_n input. When the host asserts ss_n, the agent logic immediately begins sending the transmit shift register contents to the miso output. The agent logic also captures data on the mosi input, and fills the receive shift register simultaneously. After a word is received by the agent, the host must de-assert the ss_n signal and reasserts the signal again when the next word is ready to be sent.
An intelligent host such as a microprocessor writes data to the txdata registers, so that it is transmitted the next time the host initiates an operation. A host peripheral reads received data from the rxdata register. A host peripheral can enable interrupts to notify the host whenever new data is received, or whenever the transmit buffer is ready for new data.