RM0082
RS_Telecom IP
Doc ID 018672 Rev 1
771/844
switching memory) is played on the DOUT pin. During TS511, TS511 received on the DIN
pin is stored at the 511st byte of the storage part of the switching memory while TS3 of the
previous frame (3rd byte of the reading part of the switching memory) is played on the TDM
output, allowing a phone call to be established between the caller connected on TS3 and the
one connected on TS511.
Switching introduces a delay of one frame between the reception of a data on the TDM input
and its transmission on the TDM output.
The 1024x8 memory is split in two banks of 512 8 bit wide locations. The address MSB bit
informs which bank is used to store and to play data.
The processor can not access this memory. Anyway, to inform the processor about the bank
position, the MSB bit can be read in the
Table 718: TDM_SYNC_GEN register (Offset 0x40)
When the last timeslot of a frame must be switched with the first timeslot of the next one,
(TS511 <->TS0 for instance), there is no time to store the data before reading it for playing.
A special bit in the action memory content will inform the state machine about this. Keeping
LTSS bit as '1' will directly send the last sample to the output shift register. The sample will
anyway be stored in the memory. For any timeslot, the action memory informs whether the
sample must be stored in the switching memory, the buffer memory, both or none.
Figure 87.
Illustration for TDM switching
Figure 88.
Storage in memory during an odd switched frame
Frame n
Frame n+1
ITS0
ITSx
ITS0
ITSx
ITS3
OTS3
OTS0
OTSy
OTSy
y < x
Input
Frame
Output
Frame
ITS3
Byte
Count
Readback address
IDM
IDM
Old frame Stroge area
Even frame Read area
Even frame Stroge area
Odd frame Read area