ISP1160
Embedded USB Host Controller
Philips Semiconductors
5. Prepare PTD data in µP system RAM
The communication between the HCD and the ISP1160 HC is in the form of
Philips Transfer Descriptor (PTD) data. The PTD data provides USB traffic
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 HC, the storage media is the 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.
6. 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.
7. 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.
8. HC performs USB transactions via USB bus interface
The HC performs the USB transactions with the specified USB device endpoint
through the USB bus interface.
9. HC informs HCD of the USB traffic results
The USB transaction status and the feedback from the specified 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 communication
between the HCD and the ISP1160’s USB HC. The PTD data contains information
required by the USB traffic. PTD data consists of a PTD followed by its payload data,
as shown in Figure 16.
FIFO buffer RAM
top
PTD
PTD data #1
payload data
PTD
PTD data #2
payload data
PTD
PTD data #N
payload data
bottom
MGT949
Fig 16. PTD data in FIFO buffer RAM.
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© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
Product data
Rev. 04 — 04 July 2003
19 of 88
NXP [ NXP ]
