DS2155 datasheet(179/262 Pages) DALLAS

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DS2156

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Figure 24-10 shows a case when, after the end of transmission of a cell from PHY N, no other PHY has a

cell available. Therefore, UR-ENB remains asserted as the ATM assumes a cell-available from PHY N.

With clock edge #9, it turns out that PHY N also has no cell available, as UR-SOC remains low. The

ATM then deasserts UR-ENB while the polling of the PHYs continues. With clock edge #15,

PHY N - 3 is found to have a cell for transmission. Thus, address N - 3 is applied and the PHY N - 3 is

selected with clock edge #16. Additional receive interface examples are available in [3].

Figure 24-10. End and Restart of Cell Transmission at Receive Interface

24.6.3

UTOPIA Side Receive: Direct Status Mode (Multireceive CLAV)

Up to a maximum of four PHY ports can be connected to one ATM layer. For each PHY port, the status

signals UR-CLAV and UT-CLAV are permanently available according to UTOPIA Level 1 specification.

Status signals and cell transfers are independent of each other. No address information is needed to obtain

status information. Address information must be valid only for selecting a PHY port prior to one or

multiple cell transfers. With respect to the status signals UR-CLAV and UT-CLAV, this mode of

operation corresponds to that of four individual PHY devices according to UTOPIA Level 1. With respect

to the cell transfer, this mode of operation corresponds to that as described in this document and [3]. The

ATM layer selects a PHY port for cell transfer by placing the desired port on the address lines

(UR-ADDRx, UT-ADDRx), while the enable signal (UR-ENB, UT-ENB) is deasserted. All PHY ports

only examine the value on the address lines for possible selection when the enable signal is deasserted. In

case the ATM suspends transmission for a specific PHY port during a cell transfer, no cells to/from other

PHY ports can be transferred during this time.

N-3

N+1

N-1

N+3

N-1

N-3

N+1

N+2

N-1

UR-CLK

UR-ADDRx

UR-CLAV

UR-ENB

UR-DATAx

UR-SOC

CELL RCV FROM:

PHY N

PHY N-3

POLLING

SELECTION

N-3

N+1

N-1

N+3

N-3

N+1

DETECTION

P45 P46 P47 P48

P42 P43 P44

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