PCD5096 datasheet(25/52 Pages) PHILIPS

25 / 52 page

1997 Jan 22

Philips Semiconductors

Preliminary speciﬁcation

Universal codec

PCD5096

9.6

IOM data buffers

The address space 40H to 77H in the SDR is reserved for up to 14 IOM data buffers. These buffers are used to exchange

data between the IOM-2 interface and the on-chip DSP. Each IOM data buffer consists of four 16-bit words: two words

for storing inbound data and two words for outbound data; this is shown in Fig.9

9.7

Local loop

A local call is implemented in order to loop-back data from one codec to another codec and vice-versa, as illustrated in

Fig.10. The inbound and outbound buffer are simply swapped. This is done by setting bit 8 in the correct IOM control

table word (see Section 9.5).

A local call is created by assigning one IOM data buffer to 2 codecs, whereby in one IOM control word bit 8 is set, and

in the other IOM control word bit 8 is reset.

Fig.9 Data flow between the IOM-2 interface and the DSP.

(1) IOM data buffers location is SDR: n = S

× 4 with S = B4 to B0 of the corresponding word in the IOM control table.

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MBH868

INBOUND

SDR (1)

+ 4

+ 2

OUTBOUND

IOM interface

DSP

Fig.10 Local call switching on the IOM interface.

(1) Bit 8 is set in slot 0 control word.

(2) Bit 8 is reset in slot n control word.

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odd frame

even frame

slot 0 (1)

slot n (2)

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