TCH tap: extend DL sniffing feature to support CSD modes Our debug feature for TCH DL sniffing reads the content of the DSP's a_dd_0 buffer (or a_dd_1 for TCH/H subchannel 1) at appropriate times and forwards captured bits to the host. This feature was originally implemented for TCH/FS, TCH/EFS and TCH/HS - now extend it to cover TCH/F data modes too.