XRT7250 datasheet(107/463 Pages) EXAR

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XRT7250

DS3/E3 FRAMER IC

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REV. 1.1.1

ister. The purpose of this interrupt is to let the local

µP know that the LAPD Transmitter has completed its

transmission of the LAPD Message frame (containing

the latest PMDL message) and is now ready to trans-

mit another LAPD Message frame.

A "0" in this bit-field indicates that the LAPD Message

frame Transmission Complete interrupt has not oc-

curred since the read of this register. A "1" in this bit-

field indicates that this interrupt has occurred since

the last read of this register.

NOTE: For more information on the TxLAPD Interrupt,

please see Section 3.2.6.

2.3.5.6

Transmit DS3 M-Bit Mask Register

(DS3 Applications)

Bit 7 - 5: TxFEBEDat[2:0]

These three (3) read/write bit-fields, along with Bit 4

of this register, allows the user to configure and trans-

mit his/her choice for the three (3) FEBE (Far-End

Block Error) bits in each outgoing DS3 Frame. The

user will write his/her value for the FEBE bits into

these bit-fields. The Transmit DS3 Framer block will

insert these values into the FEBE bit-fields of each

outgoing DS3 Frame, once the user has written a "1"

to Bit 4 (FEBE Register Enable).

NOTE: For more information on this feature, please see

Section 3.2.4.2.1.9.

Bit 4 - FEBE Register Enable

This Read/Write bit-field permits the user to configure

the Transmit DS3 Framer to insert the contents of

TxFEBEDat[2:0] into the FEBE bit-fields each out-

bound DS3 Frame.

Writing a "0" to this bit-field disables this feature (e.g.,

the Transmit DS3 Framer block will transmit the inter-

nally generated FEBE bits). Writing a "1" to this bit-

field enables this features (e.g., the internally gener-

ated FEBE bits are overwritten by the contents of the

TxFEBEDat[2:0] bit-field).

NOTE: For more information on this feature, please see

Section 3.2.4.2.1.9.

Bit 3 - Transmit Erred P-Bit

This Read/Write bit-field permits the user to insert er-

rors into the P-bits of the outgoing DS3 frames (via

the Transmit DS3 Framer). If the user enables this

feature, then the Transmit DS3 Framer block will pro-

ceed to invert each and every P-bit, from its comput-

ed value, prior to transmission to the Remote Termi-

nal.

Writing a "0" to this bit-field (the default condition) dis-

ables this feature (e.g., the correct P-bits are sent).

Writing a "1" to this bit-field enables this feature (e.g.,

the incorrect P-bits are sent).

NOTE: For more information on this feature, please see

Section 3.2.4.2.2.

Bit 2 - 0 M-Bit Mask[2:0]

These Read/Write bit-fields permit the user to insert

errors in the M-bits for Test and Diagnostic purposes.

The Transmit DS3 Framer automatically performs an

XOR operation on the actual contents of the M-bit

fields to these register bit-fields. Therefore, for every

'1' that exists in these bit-fields, will result in a change

of state of the corresponding M-bit, prior to being

transmitted to the Remote Terminal Equipment.

If the Transmit DS3 Framer is to be operated in the

normal mode (e.g., when no errors are being injected

into the M-bit fields of the outbound DS3 Frame), then

these bit-fields must be all “0’s”.

2.3.5.7

Transmit DS3 F-Bit Mask Register - 1

(DS3 Applications)

TXDS3 M-BIT MASK REGISTER (ADDRESS = 0X35)

BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0

TxFEBEDat[2:0]

FEBE Reg

Enable

Tx Error

P-Bit

MBit Mask[2]

MBit Mask[1]

MBit Mask[0]

R/W

000

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