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PRELIMINARY
XRT86VL38
REV. P1.0.6
OCTAL T1/E1/J1 FRAMER/LIU COMBO
88
0
E1
FASSEL
R/W
0
FAS Alignment Algorithm Select
This READ/WRITE bit field specifies which algorithm the Receive E1
Framer block uses in its search for the FAS Alignment.
0 = Setting this bit to ‘0’ selects the FAS Algorithm 1
Algorithm 1
Step 1
- Algorithm 1 begins by searching for the correct 7-bit FAS
pattern. Go to Step 2 if found.
Step 2
- Check if the FAS is absent in the following frame by verifying
that bit 2 of the assumed timeslot 0 of the Non-FAS frame is a one.
Go back to Step 1 if failed, otherwise, go to step 3.
Step 3
- Check if the FAS is present in the assumed timeslot 0 of the
third frame. Go back to Step 1 if failed.
After the first three steps (if they all passed), the Receive E1 Framer
Block will declare FAS in SYNC if Frame Check Sequence (Bit 1 of
this register) is disabled. If Frame Check Sequence (Bit 1 of this reg-
ister) is enabled, then the Receive E1 Framer Block will need to ver-
ify the correct frame alignment for an additional two frames.
1 = Setting this bit to ‘1’ selects the FAS Algorithm 2
Algorithm 2
Algorithm 2 is similar to Algorithm 1 but adds a one-frame hold off
time after the second step fails. After the second step fails, it waits for
the next assumed FAS in the next frame before it begins the new
search for the correct FAS pattern.
Step 1
- Algorithm 1 begins by searching for the correct 7-bit FAS
pattern. Go to Step 2 if found.
Step 2
- Check if the FAS is absent in the following frame by verifying
that bit 2 of the assumed timeslot 0 of the Non-FAS frame is a one.
Go back to Step 4 if failed, otherwise, go to step 3.
Step 3
- Check if the FAS is present in the assumed timeslot 0 of the
third frame. Go back to Step 1 if failed, otherwise, proceed to check
for Frame Check Sequence.
Step 4
- Wait for assumed FAS in the next frame, then go back to
Step 1
After the first three steps (if they all passed), the Receive E1 Framer
Block will declare FAS in SYNC if Frame Check Sequence (Bit 1 of
this register) is disabled. If Frame Check Sequence (Bit 1 of this reg-
ister) is enabled, then the Receive E1 Framer Block will need to ver-
ify the correct frame alignment for an additional two frames.
T
ABLE
15: F
RAMING
S
ELECT
R
EGISTER
-E1 M
ODE
R
EGISTER
7- E1 M
ODE
F
RAMING
S
ELECT
R
EGISTER
(FSR) H
EX
A
DDRESS
: 0
X
n107
B
IT
F
UNCTION
T
YPE
D
EFAULT
D
ESCRIPTION
-O
PERATION