Philips Semiconductors
ISP1160
Embedded USB Host Controller
Product data
Rev. 03 — 27 February 2003
19 of 89
9397 750 10765
Koninklijke Philips Electronics N.V. 2003. All rights reserved.
Prepare PTD data in microprocessor’s system RAM
The communication channel between the HCD and the ISP1160’s USB HC is in
the form of Philips Transfer Descriptor (PTD) data. The PTD data provides USB
trafc information about the commands, status and USB data packets.
The physical storage media of PTD data for the HCD is the microprocessor’s
system RAM. For the ISP1160’s USB HC, it is the ISP1160’s internal FIFO buffer
RAM.
The HCD prepares PTD data in the microprocessor’s system RAM for transfer to
the ISP1160’s HC internal FIFO buffer RAM.
Transfer PTD data into HC’s FIFO buffer RAM
When PTD data is ready in the microprocessor’s system RAM, the HCD must
transfer the PTD data from the microprocessor’s system RAM into the ISP1160’s
internal FIFO buffer RAM.
HC interprets PTD data
The HC determines what USB transactions are required based on the PTD data
that has been transferred into the internal FIFO buffer RAM.
HC performs USB transactions via USB bus interface
The HC performs the USB transactions with the specied USB device endpoint
through the USB bus interface.
HC informs HCD the USB trafc results
The USB transaction status and the feedback from the specied USB device
endpoint will be put back into the ISP1160’s HC internal FIFO buffer RAM in PTD
data format. The HCD can read back the PTD data from the internal FIFO buffer
RAM.
9.3 PTD data structure
The Philips Transfer Descriptor (PTD) data structure provides a communication
channel between the HCD and the ISP1160’s USB HC. PTD data contains
information required by the USB trafc. PTD data consists of a PTD followed by its
Fig 16. PTD data in FIFO buffer RAM.
MGT949
PTD
FIFO buffer RAM
payload data
PTD data #1
PTD
payload data
PTD
PTD data #2
PTD data #N
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