SY87724L

7

Micrel, Inc.

M9999-031506

hbwhelp@micrel.com or (408) 955-1690

Wide Mux

The more typical case will be to convert 8 or 10 bit wide

parallel data words into a serial bit stream. Because the

worst case parallel input rate is on the order of 250 to 340

Mega-transfers per second, single ended parallel inputs are

used.

This scenario is much like the narrow mux case, except

now MPINCK+ clocks slower, for 8 or 10 bit parallel words.

MDM

MSOUT

±

MP0-9

MPINCK+

MTXCLK

±

Figure 5. Wide Mux

Note that the input data indication is now single ended,

and that completely different input pins are used, as

compared to the 4 or 5 bit case.

The following table summarizes the available bit widths.

The right column shows the parallel input bits, such as they

will appear in the serial output stream.

Width

Sequence

4

MPF0

±, MPF1±, MPF2±, MPF3±

5

MPF0

±, MPF1±, MPF2±, MPF3±, MPF4±

8

MP5, MP6, MP7, MP8, MP0, MP1, MP2, MP3

10

MP5, MP6, MP7, MP8, MP9, MP0, MP1, MP2, MP3,

MP4

Loopback

To ease system design, the SY87724L MDM has the

capability to loop parallel data in, through the mux, into the

demux, and back to parallel data out. This permits system

check-out through to the individual MDM device. Note that,

for a full check-out, some form of loopback further down the

serial stream is required.

Loopback is incorporated into MDM by modifying the

serial clock, data, and sync inputs to the demux stage.

During loopback, the source of serial information for the

demux is changed. The MSOUT

±, MTXCLK± and

MSYNOUT

± are internally muxed to the DSIN±, DCKIN±,

and DFMIN

± nodes of the demux section. The MSYNOUT±

signal has the same characteristics as the DFMIN logic

expects.

This exercises the internal data path, both mux and

demux, for MDM, and also the control logic. The parallel

data presented to the parallel inputs will appear, some small

but unspecified time later, at the parallel outputs.

MSOUT

±

DFMIN

±

MP*

DP*

* Number of wires depends on the SIZX bits.

DCKIN

±

DSIN

±