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BM67_BS67m02
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7.5
Boot Strap Signals
Table 28 Boot Strap Signal Descriptions
Signal
Pin # Description of Boot Strap Signal
I/O
PU/PD Comment
AC/HDA_SYNC
A29
High Definition Audio Sync:
This signal is a 48 kHz fixed rate sample sync to the
codec(s). It is also used to encode the stream number.
O
3.3VSB
PU 1K
3.3VSB
AC/HDA_SYNC is a boot strap signal
(see caution statement below)
AC/HDA_SDOUT
A33
High Definition Audio Serial Data Out:
This signal is the serial TDM data output to
the codec(s). This serial output is double-pumped for a bit rate of 48 Mb/s for High
Definition Audio.
O
3.3VSB
PU 1K
3.3VSB
AC/HDA_SDOUT is a boot strap signal
(see caution statement below)
LVDS_I2C_DAT
A84
DDC lines used for flat panel detection and control.
I/O 3.3V PU 2k2
3.3V
LVDS_I2C_DAT is a boot strap signal
(see caution statement below).
SPKR
B32
Output for audio enunciator, the “speaker” in PC-AT systems
O 3.3V
SPKR is a boot strap signal (see
caution statement below)
SDVO_I2C_DAT
(SDVO_DATA)
C73
SDVO I²C data line to set up SDVO peripherals.
I/O 3.3V
SDVO_I2C_DAT is a boot strap signal
(see caution statement below)
DDPC_CTRLDATA
D64
HDMI port C Control Data
I/O 3.3V
DDPC_CTRLDATA is a boot strap
signal (see caution statement below)
DDPD_CTRLDATA
D83
HDMI port D Control Data
I/O 3.3V
DDPD_CTRLDATA is a boot strap
signal (see caution statement below)
Caution
The signals listed in the table above are used as chipset configuration straps during system reset. In this condition (during reset), they are
inputs that are pulled to the correct state by either COM Express™ internally implemented resistors or chipset internally implemented resistors
that are located on the module. No external DC loads or external pull-up or pull-down resistors should change the configuration of the signals
listed in the above table with the exception of LVDS_I2C_DAT, SDVO_I2C_DAT, DDPC_CTRLDATA and DDPD_CTRLDATA. External resistors
may override the internal strap states and cause the COM Express™ module to malfunction and/or cause irreparable damage to the module.