isp1302 NXP Semiconductors, isp1302 Datasheet - Page 13

• 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
7.9.1 Audio timer
7.9.2 TxD pulse generator
The audio timer has two main functions. The first function is to generate the timing for the
positive and negative interrupt pulses. The second function is to generate a time base that
can be used to detect a carkit interrupt while in stereo mode, and reset the RxD NRZ
signal during data-during-audio.
The TxD pulse generator is enabled when the OTG carkit transceiver is outputting
data-during-audio.
When a rising or falling edge is detected on SE0/VM, the TxD pulse generator uses the
AUD_TMR_OUT signal to perform the following sequence:
The delay between a data edge on SE0/VM and a pulse pair being output on DM will jitter
by as much as one audio timer period because the audio timer is free running. This is
acceptable because the audio timer period is between 200 ns to 500 ns, and the UART
data rate is always less than or equal to 115 kbit/s.
1. 3-state the left speaker buffer.
2. Enable the TxD buffer.
3. Output a HIGH level for the duration of the positive pulse width.
4. Output a LOW level for the duration of the negative pulse width.
5. Disable the TxD buffer.
6. Enable the left speaker buffer.
Fig 8. Audio data control
SE0/VM
DAT/VP
60 MHz
CLOCK
AUDIO
TIMER
Rev. 01 — 24 May 2007
GENERATOR
CONVERTER
TXD PULSE
INTERRUPT
RXD PULSE
DETECTOR
STEREO
USB OTG transceiver with carkit support
INTERRUPT
DETECTOR
CARKIT
TXD
RXD
004aaa629
© NXP B.V. 2007. All rights reserved.
ISP1302
DM
SPRK_L_EN
CR_INT
DP
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