DS26519 datasheet(63/310 Pages) MAXIM

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DS26519 16-Port T1/E1/J1 Transceiver

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9.9.3

T1 Transmit Synchronizer

The DS26519 transmitter can identify the D4 or ESF frame boundary, as well as the CRC multiframe boundaries

within the incoming NRZ data stream at TSERn. The TFM (TCR3.2) control bit determines whether the transmit

synchronizer searches for the D4 or ESF multiframe. Additional control signals for the transmit synchronizer are

located in the TSYNCC register. The latched status bit TLS3.0 (LOFD) is provided to indicate that a loss of frame

synchronization has occurred, and a real-time bit (LOF) which is set high when the synchronizer is searching for

frame/multiframe alignment. The LOFD bit can be enabled to cause an interrupt condition on

INTB.

Note that when the transmit synchronizer is used, the TSYNCn signal should be set as an output (TSIO = 1) and

the recovered frame-sync pulse will be output on this signal. The recovered CRC-4 multi-frame sync pulse will be

output if enabled with TIOCR.0 (TSM = 1).

Other key points concerning the E1 transmit synchronizer:

1) The Tx synchronizer is not operational when the transmit elastic store is enabled, including IBO modes.

2) The Tx synchronizer does not perform CRC-6 alignment verification (ESF mode) and does not verify

CRC-4 codewords.

The Tx synchronizer cannot search for the CAS multiframe. Table 9-16 shows the registers related to the transmit

synchronizer.

Table 9-16. Registers Related to the Transmit Synchronizer

FRAMER 1

ADDRESSES

FUNCTION

Transmit Synchronizer Control Register

(TSYNCC)

18Eh

Resynchronization control for the transmit

synchronizer.

Transmit Control Register 3 (TCR3)

183h

TFM bit selects between D4 and ESF for the

transmit synchronizer.

Transmit Latched Status Register 3

(TLS3)

192h

Provides latched status for the transmit

synchronizer.

Transmit Interrupt Mask Register 3

(TIM3)

1A2h

Provides mask bits for the TLS3 status.

Transmit I/O Configuration Register

(TIOCR)

184h

TSYNCn should be set as an output.

Note: The addresses shown above are for Framer 1.

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