Datasheet

Analog Integrated Circuit Device Data
95 Freescale Semiconductor
MC34708
Functional Block Description
Figure 25. Operating Waveforms of the Wait Bit
7.8.4.6.2 Automatic Switching OR Manual Switching (Switch_open & Manual S/W Bits)
When a supported accessory is identified, the default behavior of the MC34708 automatically turns on the corresponding signal
switches. The user can also choose to turn on optional signal switches manually. Switch turn on is controlled by the Manual 
S/W bit and the Switch_Open bits in the USB Manual SW/Result and USB Control/Device mode registers respectively.
If the Switch_Open bit is '0', the audio, UART, and USB switches are off.
If Manual S/W = 1, which is its reset value, the switches to be turned on and the outputs of the JIG and BOOT pins are determined
automatically by the Device Mode register, which is the identification result. If Manual S/W = 0, the switches to be turned on are
determined by the values of the USB Manual SW/Result register. The relationship between the values of the USB Manual SW/
Result register and the switches to be turned on is found in
SPI/I2C Register Map section.
The values of the Switch_Open and Manual S/W bits will not affect the identification flow and the timing of the signal switching
action of the MC34708. The difference between Manual S/W = 1 and Manual S/W = 0 is what switches are turned on. In both
cases, no switches are turned on in Standby mode. If the Manual S/W bit is changed from '1' to '0' while an accessory is attached,
the already automatically turned on switches will be turned off, and the switches selected manually will be turned on. However,
writing the Manual S/W bit back to '1' in Active mode will not change the switches and outputs status. Setting the
Switch_Open
= 1, sets the switches according to the Manual S/W bit.
Raw Data (Raw Data Bit)
The RAW DATA bit functions only when the accessory is Audio Type 1, which supports the remote control key. The RAW DATA
bit determines whether to report the ID pin resistance change to the baseband when any key is pressed. When RAW DATA
= 1,
the ADC is enabled only when an ID line event is detected, such as when a key is pressed. In this case, the interrupt bits KP,
LKP, or LKR, and the corresponding button bits in Button 1 and Button 2 registers, will be set accordingly. Detailed behavior
information when RAW DATA = 1 can be found in
Audio Type 1 Operation Mode.
Audio Device Type 1 - Audio with or without the Remote Control. When RAW DATA = 0, the ADC is enabled periodically to
calculate the ID line resistance. Any change of ADC Result will set the ADC_Change interrupt bit to inform the baseband. The
baseband can read the ADC result via the SPI. The KP, LKP, or LKR, and the button bits, will not set when RAW DATA = 0. The
period of ADC conversion is determined by the Device Wake-up bits in the USB Timing register. All other behaviors of Audio
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