Datasheet

AD9920A
Rev. B | Page 43 of 112
Special Pattern Insertion
Additional flexibility is available using the SPC_PAT_EN
register bits, which allow a Group B, Group C, or Group D
pattern to be inserted into a series of Group A repetitions. This
feature is useful when a different pattern is needed at the start,
middle, or end of a sequence.
Figure 54 shows an example of a sweep region using VPATA
with multiple repetitions where a single repetition of VPATB
has been added into the middle of the sequence. Figure 55
shows more detail on how to set the registers to achieve the
desired timing.
Note that VREPB is used to specify which repetition number
has the special pattern inserted instead of VPATA. VPATB
always has priority over VPATC or VPATD if more than one
SPC_PAT_EN bit is enabled (that is, SPC_PAT_EN, Bit 0 has
priority over SPC_PAT_EN, Bit 1 and Bit 2).
VD
X
V1 TO XVx
HD
REGION 1: SWEEP REGION
LINE 0 LINE 1
REGION 0 REGION 2
LINE 24 LINE 25LINE 2
SCP1 SCP2
PATTERN B INSERTED DURING PATTERN A REPETITIONS
0
6878-053
Figure 54. Special Pattern Insertion Example
X
V1
HD
V-PATTERN A
V-PATTERN B V-PATTERN A
REP 1 REP 2
REP N
REP 5REP 4REP 3
REGISTER SETTINGS: DESCRIPTION:
SPC_PAT_EN[0] = 1 V-PATTERN B IS USED AS SPECIAL PATTERN
VREPA = N TOTAL NUMBER OF REPS USED FOR SEQUENCE (N REPS)
VREPB = 4 REP 4 USES V-PATTERN B INSTEAD OF V-PATTERN A
NOTES
1. VSTARTB MUST BE SET EQUAL TO VSTARTA.
06878-054
Figure 55. Special Pattern Insertion Registers