SLWS132 Datasheet, PDF (18/46 Pages) Texas Instruments – QUAD RECEIVER CHIP

GC4014 QUAD RECEIVER CHIP
DATA SHEET REV 0.6
control counter can be synchronized to one of these sources. These syncs can also be output from the chip so that
multiple chips can be synchronized to the syncs coming from a designated “master” GC4014 chip.
3.10 DATA LATENCY
The latency through the chip, including all pipeline delays and filtering group delays, is shown in the
following table (N is the CIC filter’s decimation ratio, see Section 3.5, SI is the sync input to the chip, SO is the sync
output from the chip, and the RDY signal marks the beginning of each output frame, See Figure 10):
Table 3: Latency
FROM INPUT
SI
SI
IN[0:13] at RDY
IN[0:13] at RDY
IN[0:13] at RDY
IN[0:13] at RDY
TO OUTPUT
SO
RDY
OUT (First)
OUT (Midpoint)
OUT (Last)
OUT
(Step Response)
LATENCY
3
3.5N+9
5
22
37
86N+15
UNITS
Clocks
Clocks
Outputs
Outputs
Outputs
Clocks
COMMENT
sync in to sync out, Register settings:
OUTPUT_SYNC = 1,SO_INT_MODE =0
Sync in to first valid RDY out
Data sample input coincident with RDY, to the first output
affected by it
-to the closest midpoint output affected by IN
-to the last output affected by IN
Step function delay, step edge is input coincident with
RDY, to the step edge output
The last entry can be used to identify the group delay through the chip for time tagging events which pass
through the chip, where the time tag needs to be accurate to fractions of the output sample. Note that the overall
decimation in the complex output mode is one sample every 4N inputs. This means that the step edge will come out
21 samples plus (2N+15) clocks later. A good time tag algorithm would be to count the number of clock cycles
between the tagged input sample and the next RDY signal (the number D), and then tag the output sample that
comes 21 RDY signals later with a time tag which is adjusted by (D - 2N-15) clocks. To insure that the adjustment
is always positive, one would wait 22 RDY signals (22 outputs) and tag the sample with an adjustment of (D+2N-15)
clocks. Note that the output sample to be tagged is the sample that is output between the 22nd RDY signal and the
next RDY signal (see Figure 10).
3.11 DIAGNOSTICS
The chip has an internal ramp generator which can be used in place of the data inputs for diagnostics. An
internal checksum circuit generates a checksum of the output data to verify the chip’s operation. Section 7.7 gives
suggested checksum configurations and their expected checksums.
Besides the internal diagnostics, the chip can support board level testing, an output test configuration which
can help initial debug as well as production test is described in Section 7.8.
GRAYCHIP, INC.
- 13 -
APRIL 27, 1999
This document contains information which may be changed at any time without notice