请问关于scomm接口的问题

dapeng901

买了一个jpeg压缩的芯片，看到datasheet中的pin有几个是scomm，请教scomm接口是什么，干什么，怎么用？以下是pin的说明：
SCOMM<7> I/O When not used, this pin should be tied low.
SCOMM<6> I/O When not used, this pin should be tied low.
SCOMM<5> I/O This pin must be used in multiple chip mode to align the outputs of
two or more ADV202s. For details, see the Applications section and
the ADV202 Multichip Application application note. When not used,
this pin should be tied low.
SCOMM<4> O LCODE Output in Encode Mode. When LCODE is enabled, the output
on this pin indicates on a high transition that the last data-word for a
field has been read from the fifo. For an 8-bit interface, such as
JDATA, LCODE is asserted for four consecutive bytes and is enabled
by default.
SCOMM<3> O SPI interface: S_CSEL. When not used, this pin should be tied low.
Used only with boot mode 6.
SCOMM<2> O SPI interface: S_MO. When not used, this pin should be tied low.
Used only with boot mode 6.
SCOMM<1> I SPI interface: S_MI. When not used, this pin should be tied low.
Used only with boot mode 6.
SCOMM<0> O SPI interface: S_CLK. When not used, this pin should be tied low.
Used only with boot mode 6