stlc1510 STMicroelectronics, stlc1510 Datasheet - Page 11

• Manufacturer Part Number: stlc1510
• Description: Northenlite G.lite Dmt Transceiver
• Manufacturer: STMicroelectronics

5.0 MAIN BLOCK DESCRIPTION
The following sections describe the sequence of
functions performed by the chip
5.1 Network Interface and Controller (NIF)
The Network Interface and Controller block (NIF) is
responsible for transferring data between the
STLC1510 and the ATM network. The NIF has two
interfaces to the backplane: an 8-bit Utopia Level 2
Physical Interface (U2PHY) and a clock and data se-
rial interface (CDIF). It communicates with the rest of
the STLC1510 via the Lamba Bus. Figure 3. shows a
functional/data path block diagram of the NIF (this di-
agram does not include all glue logic between the
major functional blocks). 37 external pins are re-
quired for the U2PHY and CDIF interfaces (19 for the
Tx direction, 18 for Rx). Pins are shared between the
two interfaces, as they will not both be active at the
same time.
5.1.1 Features
Utopia Level 2 8-bit parallel interface.
Up to 9 ATM cells (477 bytes) of rate adaptation
buffering for the Utopia Level 2 TX interface.
The amount of buffering is programmable via a
memory-mapped register.
Up to 2 ATM cells (106 bytes) of rate adaptation
buffering for the Utopia Level 2 RX interface.
The amount of buffering is programmable via a
memory-mapped register.
ATM Transconvergance (TC) layer cell
processor with 16-bit data path: performs
scrambling/descrambling, HEC calculation, cell
delineation with error detection (no error
correction) and cell rate decoupling by idle cell
insertion/detection.
Clock and Data serial interface.
Implemented as a hardware module on the
Lamba bus with an 8-bit data interface and 16-
bit control interface.
4 ATM cells (212 bytes) of rate adaptation
buffering in each direction (TX and RX) for
interfacing to the Lamba bus.
Pads partial or runt cells (ATM cells of length
less than 53 bytes) to 53 bytes in the TX
direction to prevent loss of synchronization at
the CPE.
5.1.2 External Interface (Pins)
The STLC1510 connects to the ATM network via 37
external pins. These are illustrated in Figure 3. Note
that the pins TxClk and RxClk are bidirectional and,
along with UTxData[0] and URxData[0], are shared
between the CDIF and U2PHY
5.1.3 Clock and data serial Interface (CDIF)
The STLC1510 can communicate serially to an ATM
network through the CDIF. Two serial data lines, one
for the Tx path (CO to CPE), the other for the Rx path
(CPE to CO), and two respective clocks realize the
exchange of information and control signals between
the STLC1510 and the network.
The CDIF of the STLC1510 has the following at-
tributes:
Transfers data between the ATM network and the
STLC1510’s Lamba Bus
Synchronizes to the ATM network.
Provides Tx and Rx clocks to the ATM network.
Accepts idle ATM cells inserted by the ATM
network in the Tx direction. These idle cells are
used by the ATM network to adapt to the clock
provided to it by the STLC1510.
Generates clock gapping in the Tx direction.
This serves two purposes: it is a flow control
mechanism to the ATM network chip, and it can
be used for the byte alignment. In the byte-
alignment role, a clock gap longer than a pre-set
threshold indicates that the most significant bit
of a byte should be transmitted on the next
rising clock edge. This is useful for aligning data
bytes to the overhead bits inserted by the
STLC1510. In the flow control role, incoming
data is not sampled when the clock is off. The
threshold used to distinguish between byte
alignment and flow control clock gapping is
software programmable and has a range of from
0 to 65535 clock cycles (a 16 bit register stores
the value).
Generates clock gapping in the Rx direction.
This serves as a flow-control mechanism; when
there is no data available for transmission to the
backplane, the clock is shut off, ensuring that no
invalid data bits are sampled by the backplane.
STLC1510
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