isp1302 NXP Semiconductors, isp1302 Datasheet - Page 14

• Manufacturer Part Number: isp1302
• Description: Isp1302 Universal Serial Bus On-the-go Transceiver With Carkit Support
• Manufacturer: NXP Semiconductors

NXP Semiconductors
ISP1302_1
Product data sheet
7.11.1 Differential driver
7.9.3 Stereo interrupt detector
7.9.4 RxD pulse converter
7.10 Autoconnect
7.11 USB transceiver
The stereo interrupt detector generates an interrupt when the CR_INT pin has been
continuously below the carkit interrupt detector threshold for a time of t
to 100 ms); refer to USB Carkit Specification (CEA-936-A), November 2005 .
When data-during-audio mode is enabled, the RxD pulse converter converts the negative
pulses on the DP line to an NRZ signal that is output to the DAT/VP line. Each time a pulse
is received, the output on DAT/VP is inverted. If DAT/VP remains at logic 0 for a time of
t
logic 1; refer to USB Carkit Specification (CEA-936-A), November 2005 .
The HNP in the OTG supplement specifies the following sequence of events to transfer
the role of the host from the A-device to the B-device:
The OTG supplement specifies that the time between the B-device de-asserting its DP
pull-up and the A-device asserting its pull-up must be less than 3 ms. For an A-device with
a slow interrupt response time, 3 ms may not be enough to write an I
the ISP1302 to assert DP pull-up. An alternative method is for the A-device transceiver to
automatically assert DP pull-up after detecting an SE0 from the B-device.
The sequence of events is as follows: After finishing data transfers between the A-device
and the B-device and before suspending the bus, the A-device sends SOFs. The B-device
receives these SOFs, and does not transmit any packet back to the A-device. During this
time, the A-device sets the BDIS_ACON_EN bit in the ISP1302. This enables the
ISP1302 to look for SE0 whenever the A-device is not transmitting (that is, whenever the
OE_N/INT_N pin of the ISP1302 is not asserted). After the BDIS_ACON_EN bit is set, the
A-device stops transmitting SOFs and allows the bus to go to the idle state. If the B-device
disconnects, the bus goes to SE0, and the ISP1302 logic automatically turns on the
A-device pull-up. To disable the DP pull-up resistor, clear bit BDIS_ACON_EN.
The operation of the driver is described in
DAT_AUD_POL
1. The A-device sets the bus in the suspend state.
2. The B-device simulates a disconnect by de-asserting its DP pull-up.
3. The A-device detects SE0 on the bus and asserts its DP pull-up.
4. The B-device detects that the DP line is HIGH and assumes the role of the host.
(20 ms to 30 ms), then the output on DAT/VP will automatically return to
Rev. 01 — 24 May 2007
Table
USB OTG transceiver with carkit support
5.
2
PH_STLO_DET
C-bus command to
© NXP B.V. 2007. All rights reserved.
ISP1302
(30 ms
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