![](http://datasheet.mmic.net.cn/330000/PM6344-RI_datasheet_16444359/PM6344-RI_220.png)
STANDARD PRODUCT
PMC-Sierra, Inc.
PM6344 EQUAD
PMC-951013
ISSUE 5
QUADRUPLE E1 FRAMER
207
end of the FIFO registers, and then disengages. Should variations in the
frequency of input clock or the output clock cause the read pointer to drift to
within one unit interval of FIFO overflow or underflow, the pointer will be
incrementally pushed away by the LIMIT control without any loss of data.
With SYNC disabled, CENT and LIMIT enabled, the maximum tolerable phase
difference between the bursty input clock and the smooth TCLKO is 40UI. Phase
wander between the two clock signals is compensated for by the LIMIT control.
13.5.3
Elastic Store Application
In multiplex applications where the jitter attenuation is not required, the DJAT
FIFO can be used to provide an elastic store function. For example, in a M12
application, the data is written into the FIFO at 2.048MHz and the data is read
out of the FIFO with a gapped E2 rate clock applied on TCLKI[x]. In this
configuration, the Timing Options OCLKSEL[1:0] bits should be programmed to
01, the TCLKISEL bit should be programmed to 1, and the SMCLKO bit should
be programmed to 1. Also, the DJAT SYNC and LIMIT bits should be disabled
and the CENT bit enabled. This provides the maximum phase difference
between the input clock and the gapped output clock of 40UI. The maximum jitter
and wander between the two clocks is 8UIpp.
13.5.4
Alternate TCLKO Reference Application
In applications where TCLKO[x] is referenced to an Nx8 kHz clock source applied
on TCLKI[x], DJAT can be configured by programming the output clock divisor,
N2, to FFH and the input clock divisor, N1, to the value (N-1). The resultant input
clocks to the phase comparator are both 8kHz. The DJAT SYNC and LIMIT bits
should be disabled in this configuration.