isp1504c NXP Semiconductors, isp1504c Datasheet - Page 46

• Manufacturer Part Number: isp1504c
• Description: Ulpi Hi-speed Universal Serial Bus On-the-go Transceiver
• Manufacturer: NXP Semiconductors

NXP Semiconductors
ISP1504A_ISP1504C_1
Product data sheet
9.14 Aborting transfers
9.15 Avoiding contention on the ULPI data bus
The ISP1504 supports aborting transfers on the ULPI bus. For details, refer to UTMI+ Low
Pin Interface (ULPI) Specification Rev. 1.1 , Section 3.8.4.
Because the ULPI data bus is bidirectional, avoid situations in which both the link and the
PHY simultaneously drive the data bus.
The following points must be considered while implementing the data bus drive control on
the link.
After power-up and clock stabilization, default states are as follows:
When the ISP1504 wants to take control of the data bus to initiate a data transfer, it
changes the DIR value from LOW to HIGH.
At this point, the link must disable its output buffers. This needs to be as fast as possible
so the link must use a combinational path from DIR.
The ISP1504 will not immediately enable its output buffers, but will delay the enabling of
its buffers until the next clock edge, avoiding bus contention.
When the data transfer is no longer required by the ISP1504, it changes DIR from HIGH to
LOW and starts to immediately turn off its output drivers. The link senses the change of
DIR from HIGH to LOW, but delays enabling its output buffers for one CLOCK cycle,
avoiding data bus contention.
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The ISP1504 drives DIR is LOW.
The data bus is input to the ISP1504.
The ULPI link data bus is output, with all data bus lines driven to LOW.
Rev. 01 — 19 October 2006
ISP1504A; ISP1504C
ULPI HS USB OTG transceiver
© NXP B.V. 2006. All rights reserved.
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