RS_Telecom IP
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Figure 89.
Storage in memory during an even switched frame
34.4.7 Buffer
memory
Buffer memory allows bufferization of upto 16 channels. It contains two banks:
●
one available for the TDM state machine,
●
the other one for the AHB.
Each bank has a capacity of 16KB (total memory size is 32KB).
Timeslots that must be stored/played are declared in the action memory. This is done
separately for the input and the output. For instance, during DTMF dialing, you don't need to
play anything.
Buffers banks, unlike switching memory, do not switch at the frame rate but at the packet
rate (usually 10ms, 20ms, or 30ms rate). A packet consists of a number of frames given by
the
Table 717: TDM_Frame_NBR register (Offset 0x3C)
.
Number of frames per packet must be same for all channels. Hence, if some channels
require 20ms packets size and others 30ms packet size, 10ms packet size will have to be
selected, and the longest packet size requirement will be fulfilled with 3 transfers to the
external memory. However, it is possible to manage packets greater than 30 ms by reducing
the number of channels. The buffer bank becomes full after the last timeslot of the last frame
has been written in the buffer bank. Banks are switched and an interrupt is raised
Inside a buffer bank, memory pointer increases differently for each frame, according to the
kind of channel:
Switching
Memory
IDM TX
IDM
2048*8
Memory
