Datasheet

Analog Integrated Circuit Device Data
91 Freescale Semiconductor
MC34708
Functional Block Description
Figure 21. Identification Flow State Diagram
7.8.4.3 Id Identification
A comparator monitors the ID pin impedance to ground. When a resistor less than 1.0 M is connected between the ID line and
the ground, the ID_FLOATS bit in the Interrupt Sense 0 register will be set to 0. When the resistor is removed, the ID_FLOATS
bit will be set to 1. A falling edge of this bit starts the identification flow, and a rising edge starts the detachment detection flow.
The ID_DET_END signal is used to indicate the end of the identification.
After the ID_FLOATS bit is set to 0, the identification flow is started, and an ADC_EN signal is set to enable an ADC conversion.
A 5-bit ID ADC is used to measure the ID resistance. The ADC is also used to identify what button is pressed in a cord remote
control when the attached accessory is an Audio Type 1 cable.
When the conversion completes, an ADC_STATUS bit is set and the ADC result value is sent to the ADC Manual SW/Result
register. The ADC_EN signal is cleared automatically after the conversion finishes.
If the ID resistance is below 2.0 k, the ADC Result is set to 00000. If the ID line is floating, the ADC Result is set to 11111.
7.8.4.4 Stuck Key Identification
When the ADC conversion is finished and the ADC result is found to be a value corresponding to a remote control key of Audio
Type 1 cable, a stuck key process flow will be initiated to determine whether a remote control key is stuck and to inform the
baseband of the stuck key status.
Figure 22 shows the stuck key process flow. If the stuck key is detected to be released within 1.5 s, the flow will return to re-start
the ID identification flow. Otherwise, a Stuck_Key Interrupt is set. When the key is released, a Stuck_Key_RCV Interrupt is
generated, and the identification flow is re-started to determine the ID resistance of the attached cable.
VBUS_DET?
Detection
Delay
USB host
USB-OTG
R
ID
= USB
jig w/ Boot?
USB jig
cable w/
boot option
Unknown
ID_FLOAT?
R
ID
< 100?
R
ID
= 75?
Video
cable
Start ADC to
measure R
ID
R
ID
= UART
jig w/ boot?
R
ID
= Audio
Type 1 ?
Audio
Type 1
R
ID
=
102k?
Phone
Powered
Device
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
R
ID
= Video
cable?
No
Yes
R
ID
= USB
jig w/o Boot?
USB jig
cable w/o
boot option
Yes
No
UART jig
cable w/
boot option
R
ID
= UART
jig w/o boot?
Yes
No
UART jig
cable w/o
boot option
R
ID
= TTY
Converter?
TTY
Converter
Yes
R
ID
= UART
Cable?
UART
Cable
Yes
No
No
DP  0.6V
DM < 0.4V?
Yes
No
DM > 0.8V
No
Yes
No
ID_FLOAT?
Yes
ID_FLOAT?
No
Yes
A/V_CHG = 1
ID_DET_EN
D?
Yes
No
Standby
Active
(Identification
Flow)
R
ID
= Audio
Type2
Cable?
Audio
Type2
Cable
Yes
Dedicated
Charger
R
ID
=
440k?
R
ID
=
200k?
5-Wire
Charger
No
Yes
Yes
No
No
ID_FLOAT
ID_DET_EN
D?
Yes
No
Yes
DM  0.6V
DP < 0.4V?
No
Yes
USB
Charger
ADC = 00000
No
R
ID
= remote
key?
No
Yes
Stuck Key
Process
ID_DET_EN
D?
No
Yes
Video cable?
Yes
No
Reset