Ravi,
The SACCH multiframe associated to SDCCH have a periodicity of 470.2ms
The SACCH multiframe associated to TCH have a periodicity of 480ms
A SACCH multiframe contains actually 4 little blocks (called SACCH blocks). These blocks are transparent for you, the system needs the four consecutive blocks in order to decode the content of the SACCH multiframe.
The content of a SACCH multiframe varies, it depends on which path it is :
DOWNLINK : It contains the System Information messages (list of neighbours, some cell parameters, etc. for instance)
UPLINK : It contains the Measurement reports from the mobile (RXLEV, RXQUAL, MS POWER, RXLEV of neighbours, etc.)
You may be a little bit confused ? Read carefully my answer, it’s all there…