IDLE
Sequence #3
TX State RX State
Sequence #1
Sequence #2
Functional Description
www.ti.com
16.3.8.1.1.4 Endpoint 0 States: Peripheral Mode
When the USB controller is operating as a peripheral device, the endpoint 0 control needs three modes –
IDLE, TX and RX – corresponding to the different phases of the control transfer and the states endpoint 0
enters for the different phases of the transfer (described in later sections).
The default mode on power-up or reset should be IDLE. RXPKTRDY bit of PERI_CSR0 (bit 0) becoming
set when endpoint 0 is in IDLE state indicates a new device request. Once the device request is unloaded
from the FIFO, the controller decodes the descriptor to find whether there is a data phase and, if so, the
direction of the data phase of the control transfer (in order to set the FIFO direction). See Figure 16-3.
Depending on the direction of the data phase, endpoint 0 goes into either TX state or RX state. If there is
no Data phase, endpoint 0 remains in IDLE state to accept the next device request
The actions that the CPU needs to take at the different phases of the possible transfers (for example,
loading the FIFO, setting TXPKTRDY) are indicated in Figure 16-4.
Figure 16-3. CPU Actions at Transfer Phases
1704
Universal Serial Bus (USB) SPRUH73H–October 2011–Revised April 2013
Submit Documentation Feedback
Copyright © 2011–2013, Texas Instruments Incorporated
To Next Page
Loading...
Need help?
General
