TI中文支持网在F2808做SPI从站时，手册中描述的都是片选信号
低电平有效，而在引脚复用时，此信号的表示方式为SPISTE，那么此时是高电平有效吗？
mangui zhang：以手册为主SPISTE低电平片选
在F2808做SPI从站时，手册中描述的都是片选信号低电平有效，而在引脚复用时，此信号的表示方式为SPISTE，那么此时是高电平有效吗？
Seven Han：The SPISTE pin operates as the slave-select pin. An active-low signal on the SPISTE pin allows the slave
SPI to transfer data to the serial data line; an inactive- high signal causes the slave SPI serial shift register
to stop and its serial output pin to be put into the high-impedance state. This allows many slave devices to
be tied together on the network, although only one slave device is selected at a time.
