RS_Telecom IP
RM0082
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Doc ID 018672 Rev 1
the DIN pin). Switching data is stored in a single port Switching Memory without access
from AHB.
●
Bufferization means that data from DIN pin (one to four timeslots per channel per
frame) is stored in the buffer memory during a programmable number of frames (please
refer to
Table 717: TDM_Frame_NBR register (Offset 0x3C)
) and data from buffer
memory is played at the same time. The buffer memory is shared between the module
and the AHB and split into two banks. Up to 16 channels (buffers) can be stored/played
from different locations (dynamically partitioned) in the buffer memory bank. Using 16
channels of 4 bytes per frame allows 30ms data storage for each channels as required
by VoIP applications.
34.4.5 Action
memory
Action memory is the heart of the state machine sending and recovering data from TDM
bus. Each word contains the information of what to do with the relative Timeslot (byte).
Action memory consists of 512 words of 32 bits each. Word0 informs about timeslot0 and
similarly word 511 informs about timeslot 512.
The options that can be chosen for the timeslot include switching Timeslot x of DIN to
Timeslot y of DOUT, bufferizing DIN and/or playing a buffer on DOUT or doing nothing.
The TDM behavior is based on three memories:
●
The action memory for information,
●
The switching memory for switching (target is small PABx),
●
The buffer memory for bufferization (target is VoIP voice buffers).
According to the content of the action memory, an incoming sample may or may not be
stored. Destination can be either the switching memory, or the buffer memory, or both.
In the reverse direction, the TDM output can be in low impedance or high impedance on a
timeslot basis. When in low impedance, DOUT can play the data from the switching memory
or from the buffer memory according to the information in the action memory.
Switching memory is only accessible by the TDM state machine on the TDM side, both in
read and write mode. The aim of the switching memory is to switch an input timeslot of a
frame to an output timeslot during the next frame. Please read
for full description.
Buffer memory is organized in two banks (16KB each). One bank can be accessed by the
TDM state machine while the other bank is available for the AHB interface. Each bank is
split into locations for N channels (with 1=< N =<16). The bank that is available for the TDM
side will play data from the all the channels to pre-defined timeslots at each frame and store
the incoming data of the same timeslot in the same place. Each time the banks are
switched, an interrupt request can be initialized by the RAS. Please read
for full description.
34.4.6 Switching
memory
Switching feature uses total memory of 1024 locations, each 8 bit wide. Switching means
that all the input timeslots of a frame received on the TDM are stored in the memory and at
the next frame, this data will be sent on the timeslot that is required to be switched.
Consider an example of switching: TS3 is switched with TS511. It means that during TS3,
the TS3 content received on the DIN pin is stored at the 3rd byte of the storage part of the
switching memory while TS511 of the previous frame (511st byte of the reading part of the