STLC60135 datasheet(16/25 Pages) STMICROELECTRONICS

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T5,T7

D98TL331

CLOCK

SIGNAL

(highz)

SIGNAL

(at input)

T6,T8

T11

T12

T10

Figure 19. Timing Specification (Utopia 1)

PHY

RECEIVE

ATM

RECEIVE

PHY

TRANSMIT

ATM

TRANSMIT

ATM

PHY

RxADDR

RxCLAV

RxENB*

RxCLK

RxDATA

RxSOC

RxREF*

TxADDR

TxCLAV

TxENB*

TxCLK

TxDATA

TxSOC

TxREF*

D98TL329

Figure 20. Signal at Utopia Level 2 Interface

DIGITAL INTERFACE

Utopia Level 2 Interface

The ATM forum takes the ATM layer chip as a

reference. It defines the direction from ATM to

physical layer as the Transmit direction. The di-

rection from physical layer to ATM is the Receive

direction. Figure 20 shows the interconnection

between ATM and PHY layer devices, the op-

tional signals are not supported and not shown.

The UTOPIA interface transfers one byte in a sin-

gle clock cycle, as a result cells are transferred in

53 clock cycles.

Both transmit and receive interfaces are synchro-

nized on clocks generated by the ATM layer chip,

and no specific relationship between Receive and

Transmit clock is assumed, they must be re-

garded as mutually asynchronous clocks. Flow

control signals are available to match the band-

width constraints of the physical layer and the

ATM layer. The UTOPIA level 2 supports point to

multipoint configurations by introducing on ad-

dressing capability and by making a distinction

between polling and selecting a device:

- the ATM chip polls a specific physical layer chip

by putting its address on the address bus when

the Enb* line is asserted. The addressed physical

layer answers the next cycle via the Clav line re-

flecting its status at that time.

- the ATM chip selects a specific physical layer by

putting its address on the address bus when the

Enb* line is deasserted and asserting the Enb*

line on the next cycle. The addressed physical

layer chip will be the target or source of the next

cell transfer.

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