
XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
182
6.3.3.4.1
There are occasions when the user may wish to in-
ject errors into the B1 byte of the PLCP frame in or-
der to verify that the Far-End Receiving hardware is
Inserting Errors into the B1 Byte
functioning properly and will detect these errors and
respond accordingly. The UNI allows the user to in-
ject these errors into the B1 byte via the TxPLCP
BIP-8 Error Mask Register, as depicted below.
The B1 (BIP-8) byte of a PLCP frame is always XORed
with this mask byte. The results of this operation are
written back into the B1-byte position, prior to trans-
mission. The user can insert an error into a particular
bit of a B1 byte, by writing a “1” into the corresponding
bit in this register.
Note:
This register must be 00h for normal operation. This
register is of value 00h following power up or reset.
6.3.3.4.2
The UNI allows the user to insert errors into each of
the “Frame Alignment” bytes A1 and A2. The user
can insert these errors by writing the appropriate da-
ta to the “Tx PLCP A1 Byte Error Mask Register (Ad-
dress = 48h); and the “Tx PLCP A2 Byte Error Mask
Register (Address = 49h). The bit formats of these two
registers follows.
Inserting Errors into the A1, A2 Bytes
The UNI IC automatically takes each A1 byte from
within an outbound PLCP frame, and performs an
XOR operation with the contents of the “Tx PLCP A1
Byte Error Mask” Register. The results of this opera-
tion are written back into the A1 Byte fields of the
PLCP frame, prior to transmission.
The UNI IC also performs the same set of operations
on the A2 bytes of the PLCP frame, with the “Tx PLCP
A2 Byte Error Mask” register.
Therefore, if the user does not wish to insert errors
into the A1 and A2 byte fields of each outbound PLCP
frame, he/she must insure that these two registers
contain the value 00h (the default value).
6.3.3.5
Manipulating the FEBE-Nibble Field
within the G1 Bytes
The UNI allows the user to either transmit G1 bytes
with a FEBE value of ‘0h’, or to transmit a G1 byte with
the correct FEBE count, as determined by the “Near-
End” Receive PLCP Processor.
The user can exercise this option by writing the ap-
propriate data to bit 4 of the Tx PLCP G1 Byte Register
(Address = 4Bh). The bit-format of this register is
presented below.
Tx PLCP BIP-8 Error Mask Register, Address = 4Ah
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
B1 Error Mask
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Tx PLCP A1 Byte Error Mask Register (Address = 48h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
A1 Error Mask
0
0
0
0
0
0
0
0
Tx PLCP A2 Byte Error Mask Register (Address = 49h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
A2 Error Mask
0
0
0
0
0
0
0
0