saf1761 NXP Semiconductors, saf1761 Datasheet - Page 146

• Manufacturer Part Number: saf1761
• Description: Hi-speed Universal Serial Bus On-the-go Controller
• Manufacturer: NXP Semiconductors

NXP Semiconductors
18. Appendix
SAF1761_1
Product data sheet
18.1.3.1 Software retry mechanism
18.1.1 Problem description
18.1.2 Implication
18.1.3 Workaround
18.1 Errata added on 2009-04-20
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description” .
When the SAF1761 is programmed to perform infinite retries on Not Acknowledged
(NAK) IN tokens, the SAF1761 does not generate the retry IN tokens on its own.
According to the SAF1761 data sheet, if register RL is programmed as zero, NakCnt is
ignored. This means that irrespective of the value of NakCnt, the SAF1761 must retry
indefinitely because there is no NakCnt to limit the number of retries for a NAK IN token.
The SAF1761 hardware, however, does not retry the NAK IN token.
After an IN token is seen on the USB bus and is NAK-ed by the downstream device, the
SAF1761 will not perform any automatic retry. Instead an interrupt will be generated in the
ATL_IRQ bit of the HcInterrupt register (310h), and the software must refresh the IN token
Proprietary Transfer Descriptor (PTD) for the retry to occur on the USB bus. This causes
the software to constantly service this retry, unless the application instructs it to stop
retrying.
Set program register RL = 1111b and NakCnt = 1111b. In this case, interrupt will be
generated when NakCnt reaches zero and the software has to reload the transfer
descriptor.
Fig 29. Temperature profiles for large and small components
temperature
MSL: Moisture Sensitivity Level
Rev. 01 — 18 November 2009
= minimum soldering temperature
maximum peak temperature
minimum peak temperature
= MSL limit, damage level
Hi-Speed USB OTG controller
temperature
peak
SAF1761
© NXP B.V. 2009. All rights reserved.
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