
MT9072
Advance Information
58
6.2.1
The pin (TxDL, TxDLC, RxDL and RxDLC) enable bits Sa4SS to Sa8SS of control register address Y08
determine the type of data link access enabled. A ’01’ code enables the corresponding data link (DL) bits to be
sourced to and from the RxDL and TxDL pins, by enabling the corresponding pulses in either gapped clocks or
enable low signals provided at the RxDLC and TxDLC pins. The option of either gapped clock or enable signal
is selected by control bit DLCK (register address Y08). The data link bits are transmitted on and received from
the PCM30 link, in the national bit (Sa4 to Sa8) positions (four to eight of timeslot zero) of the Non-Frame
Alignment Signal (NFAS) frames. The gapped clock rate will be either 4, 8, 12, 16 or 20kb/s, and will depend on
the number of Sa bits enabled by SA#SS bits (register Y08). Similarly the enable pulse width(s) will also
depend on the number of Sa bits enabled.
E1 Data Link (DL) Pin Access
6.2.1.1 E1 Data Link (DL) Pin Data Transmitted on PCM30
Data to be transmitted onto the line in the S
a
bit position is clocked in from the TxDL pin with the TxDLC clock.
Although the aggregate clock rate equals the bit rate, it has a nominal pulse width of 244 ns, and it clocks in the
TxDL as if it were a 2.048Mbit/s data stream. The clock can only be active during bit times 4 to 0 of the ST-BUS
frame. The TxDL input signal is clocked into the MT9072 by the falling edge of TxDLC which occurs about 3/4
into the ST-BUS bit cell. If DL bits are selected to be accessed through the DL pins, then all other programmed
functions for those S
a
bit positions are overridden. See Figures 59 & 60 for timing requirements.
6.2.1.2 E1 Data Link (DL) Pin Data Received on PCM30 - With No Elastic Buffer
The RxDLC clock and enable signal is derived from the receive extracted clock (EXCLi) and is aligned with the
receive data link output RxDL. The HDB3 decoded receive data, at 2.048Mbit/s, is clocked out of the device on
the RxDL pin with the falling edge of EXCLi. In order to facilitate the attachment of this data stream to a Data
Link controller, the clock signal RxDLC consists of positive pulses, of nominal width of 244 ns, during the S
a
bit
cell times that are selected for the data link, with the rising edge aligned with the middle of the bit cell. No DL
data will be lost or repeated when a receive frame slip occurs as the DL data does not pass through the elastic
buffer. The output signal at the RxDLC pin may be either a clock or an enable signal as programmed by the
DLCK control bit (register address Y08). See Figures 62 & 63 for timing requirements.
Register
Address
Register
Description
Y00
Alarm and Framing Control
Register
The Data Link is not supported in the IMA mode.
Y06
HDLC and CCS ST-BUS
control register
The bit HPSEL has to be 0 if the internal HDLC is to be used for the
Data Link.
Y08
Data Link Control Register
This register determines the source of the Sa bits which can be micro
port,HDLC, data link pins or ST-BUS. This register is also used to
control the data link pins Txdl and Rxdl.
Y13
NFAS and FAS status
The national use bits RNU can be read from this status register.
Y26
CAS, National, CRC-4
Latched Status
The Sa bit latched values can be read from this register, SA5VL,
SA6NL etc.
Y36
CAS, National, CRC-4
Interrupt Status
The Sa bit interrupt values can be read from this register, SA5VI,
SA6NI etc.
Y46
CAS, National, CRC-4
Interrupt Mask
These are the mask bits for Y36.
YB0-YB4
Transmit National Bits
Transmit national bits used for sending
Sa bits(SA4 to SA8).
YC0-YC4
Receive national bit
Receive National bits(SA4 to SA8)
Table 17 - Data Link and Sa bits Configuration and Status Registers (E1)