| 摘要 |
<p>A protocol may enable support of the USB 2.0 LPM (Link Power Management) Addendum by a ULPI PHY (Universal Serial Bus Transceiver Macrocell Low-Pin Interface Physical Layer Device), facilitating transmitting the reserved PID (Physical Interface Device) token, used in the LPM Extended Transaction, through a ULPI bus. Bits [3:0] of a ULPI Tx Cmd (Transmit Command) byte may be reused, with the value of those bits being 4'b0 for a transmission (normally indicating a No PID transmission), by configuring the ULPI PHY to qualify the selected four Tx Cmd bits (bits [3:0] of the Tx Cmd) with the Opmode code. The ULPI PHY may thereby interpret bits [3:0] of the Tx Cmd byte based on the value of the Opmode, and may not transmit the Extended PID when the Opmode is set to 2'b10, that is, when the Opmode is indicative of bit-stuffing and NRZI encoding being disabled, for example during a Chirp transmission. When the Opmode code is set to 2'b0, indicative of normal bit-stuffing, and the Tx Cmd bits [3:0] are set to 4'b0 during a transmission (Tx Cmd bits[7:6] = 2'b01), then the PHY may transmit the Extended PID, followed by the rest of the extended transaction onto a USB.</p> |
