Datasheet

Analog Integrated Circuit Device Data
97 Freescale Semiconductor
MC34708
Functional Block Description
7.8.4.8 Audio Type 1 Operation Mode
Audio Type 1 accessories have the same interface shown in Figure 27, either stereo or mono, with or without a remote control,
or with or without a microphone. When a device, such as a microphone is not connected to the accessory, the corresponding pin
in the mini-USB connector will be left floating. With the normal operation setting of the control bits, the accessory is identified as
an Audio Type 1 device, the analog switches SW4 and SW7 for SPK_R to DP, SPK_L to DM, and SW5 for VBUS to MIC are
turned on, and the MOTG, and M0 switches are turned off, to isolate the VBUS pin.
The MC34708 supports the remote control key for an Audio Type 1 device. If the RAW DATA = 0, the ADC is turned on
periodically to monitor the ID line change caused by the key press. The period is programmed by the Device Wake-up bits. If the
ADC Result changes, the ADC_Change bit in the USB Interrupt Sense register is set to inform the baseband. If the RAW
DATA
= 1, a comparator is enabled to monitor the key press. The timing of the key press when RAW DATA = 1 is shown in
Figure 28. If a key is pressed for a time less than 20 ms, the MC34708 ignores it. If the key is still pressed after 20 ms, the
MC34708 starts a timer to count the time during which the key is kept pressed. There are three conditions according to the press
time: Error key press, short key press, and long key press.
1. Error key press: if the key press time is less than TKP, the Error bit in the USB Button register and the short key press bit
KP in USB Interrupt Sense register are set to indicate an error has occurred. The Error bit is reset to '0' when the USB
Button register is read or the next key press occurs. The KP bit is cleared when the Interrupt 1 register is read.
2. Short key press: if the key press time is between TKP and TLKP, the KP bit and the corresponding button bit in USB
Button are set to inform the baseband. If the ADC result is not one of the ADC values of the 13 buttons, the Unknown bit in
the Button register is set. The INT pin is driven high when the key is released and returns to low when the interrupt register
is read. The KP bit is cleared when the USB Interrupt Sense register is read.
3. Long key press: if the key press time is longer than TLKP, the long key press bit LKP in the USB Interrupt Sense register,
and the corresponding button bit, are set to inform the baseband. If the ADC Result is not one of the ADC values of the 13
buttons, the Unknown bit in the USB Button register is set. When the key is released, the long key release bit LKR in the
Interrupt Status 0 register is set to interrupt the baseband again.
Figure 27. Audio Accessory with Remote Control and Microphone
Table 93. Switch Configuration When Controlled by the Device Type Register
Device Type Audio USB UART USB CHG Dedicated CHG
On SW# 4, 5, 7 3, 6, 1, 2 3, 6 -
Off SW MOTG, M0 -
(69)
- -
Device Type 5WT1 CHG 5WT2 CHG JIG_USB_ON
JIG_USB_OFF
JIG_UART_ON
JIG_UART
TTY
On SW# - - 3, 6 3, 6 4, 5, 7
Off SW - - -
(69)
MOTG, M0
Notes
69. Switches M0, M1, and MOTG are controlled by software by the OTGEN and VUSBSEL bits.