EMC12 ETC2 [List of Unclassifed Manufacturers], EMC12 Datasheet - Page 28

• Manufacturer Part Number: EMC12
• Description: Audio Interface for the EmPack System
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

The normal TDM map connections using the Option1 modes of TDM_DATA, TDM_CONTINUE and
TDM_CONDITIONAL are self explanatory. However the TDM_DSP_VALID and
TDM_C12DSP_OLD modes may require some further explanation.
Section 3.4.4 describes how the programmable TDM validity mode, TDM_DSP_VALID, works at the
hardware level. Below is an example of setting up a TDM map for this mode using the API functions.
In the example, a TDM map is built for an EMC12 DSP to transmit data and control the valid line on 4
TDM slots. The DSP will synchronize to the TDM frame and begin sending 4 16-bit words per frame.
Each 16-bit word has the TDM valid information in the upper 8-bits and the TDM data is in the lower 8-
bits.
With this TDM map loaded, the DSP will receive 4 OLD pulses per frame, at the beginning of time slots
4, 8, 12 and 16. The EMC12 hardware receive 16 bits from the DSP’s serial output port during time slot
pairs 4/5, 8/9, 12/13 and 16/17. The first 8 bits of each pair is the validity information, which is actually
encoded in the 2nd bit received. This information is held until the second slot of each pair when it is used
to drive the TDM valid line to coincide with the TDM data. No TDM data or valid is driven from the
DSP during the first slot of each pair and, although the second time slot of each pair is encoded as
TDM_DATA mode, the DSP only receives an OLD pulse for the time slots encoded as
TDM_DSP_VALID.
Example 2:
There may arise a need to temporarily replace one or more of the time slots transmitted from the DSP
with data from another source such as a Codec on the same EMC12 mezzanine or a DSP or Codec on
another mezzanine. However, with DSP transmitting on a fixed number of time slots, synchronized to the
TDM frame, the OLD pulses to the DSP should remain constant. When using TDM_DSP_VALID
mode it is possible to maintain the OLD pulses that occur at the beginning of the time slots designated for
the valid information, yet not have the valid information or the data portion of the DSP’s 16-bit serial
output driven onto the TDM bus.
In the example, below, the map using TDM_DSP_VALID mode from the previous example will be
modified. Sometime after that map has been in use the data from the DSP will be replaced on time slot 9
by data from a Codec and on time slot 13 by data from a device on another mezzanine. The following
function calls make the necessary changes to the map on the EMC12 mezzanine.
09 Jan 2006
MODULE_HANDLE
RESOURCE_HANDLE
int
EmAddTdmSrc(emc12, dsp,
EmAddTdmSrc(emc12, dsp,
EmAddTdmSrc(emc12, dsp,
EmAddTdmSrc(emc12, dsp,
EmAddTdmSrc(emc12, dsp, 12, tdm_bus, TDM_DSP_VALID, 0);
EmAddTdmSrc(emc12, dsp, 13, tdm_bus, TDM_DATA, 0);
EmAddTdmSrc(emc12, dsp, 16, tdm_bus, TDM_DSP_VALID, 0);
EmAddTdmSrc(emc12, dsp, 17, tdm_bus, TDM_DATA, 0);
EmStartTdm(emc12);
emc12;
dsp;
tdm_bus = TDM_BUSA;
Communication Automation Corporation
EMC12 Hardware Reference Manual
4, tdm_bus, TDM_DSP_VALID, 0);
5, tdm_bus, TDM_DATA, 0);
8, tdm_bus, TDM_DSP_VALID, 0);
9, tdm_bus, TDM_DATA, 0);
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