T8207 Datasheet, PDF (45/158 Pages) Agere Systems – ATM Interconnect

Advance Data Sheet
September 2001
CelXpres T8207
ATM Interconnect
9 UTOPIA Interface (continued)
9.2.2 Outgoing ATM Mode (Cells Sent by T8207)
In ATM mode, the T8207 may connect to PHY devices that either meet level 1 or level 2 UTOPIA specifications. If
connection is to devices that meet only UTOPIA level 1 specifications, the T8207 may access up to four of these
PHY devices using the four enable (u_txenb*[3:0]) and cell available (u_txclav[3:0]) signals. Polling of the cell
available signals occurs while the current cell is transmitted.
If the T8207 connects to PHY devices meeting level 2 UTOPIA specifications, one TxCLAV/TxENB pair supports
up to 16 PHY ports. For 32 PHY ports, two TxCLAV/TxENB pairs support two groups of 16 PHY ports for a total of
32 PHY ports.
In ATM MPHY mode, the u_txdata[7:0], u_txaddr[4:0], u_txsoc, and u_txprty outputs are connected to each PHY
port. In addition, the T8207 generates the address (u_txaddr[4:0]) signals, permitting selection and arbitration
among the ports. The number of address lines used in the connection may vary from one to four giving a maximum
address value of 15. (All five address lines must be connected to provide for the NULL address.) Refer to Section
9.6, UTOPIA Pin Modes, for more information about the possible combinations of address, cell available, and
enable signals. The UTOPIA specification for operation with one TxClav and one RxClav is used when the T8207
connects to multiple UTOPIA level 2 PHY devices.
In ATM mode, all unused u_txclav inputs require connection to ground.
Note: The u_txenb outputs are high impedance during powerup and reset. An attached PHY may interpret this
high-impedance state as an enable; however, the T8207 is not ready to send data during this time. Attach
pull-up resistors to these outputs if a problem is anticipated.
The TX UTOPIA cell buffer holds the next cells to be transmitted onto the UTOPIA bus. This TX UTOPIA cell
buffer, which holds 128 cells, may be divided into 1, 4, 8, 16, 32, or 64 queues using the div_queue bits in the main
configuration 2 register (address 0112h). The number of ports that the T8207 supports determines the number of
queues that should be chosen. (See Section 9.6, UTOPIA Pin Modes.) The number of cells per queue, held by the
buffer, is determined by dividing 128 (maximum number of cells that TX UTOPIA cell buffer holds) by the number of
queues selected (e.g., two cells per queue for 64 queues and 32 cells per queue for 4 queues).
If the T8207_sel bit in the main configuration 2 register, Table 59, is set, each port is assigned four queues in the
TX UTOPIA cell buffer except in the case of 32 ports. For 32 ports, each port is assigned two queues. Each group
of four queues is priority encoded where the lowest-numbered queue has the highest priority. Groups of four
queues are shared among two ports as follows:
s Queues 0—3 are shared between ports 0 and 1.
s Queues 4—7 are shared between ports 2 and 3.
s Queues 8—11 are shared between ports 4 and 5.
s Queues 12—15 are shared between ports 6 and 7.
s Queues 16—19 are shared between ports 8 and 9.
s Queues 20—23 are shared between ports 10 and 11.
s Queues 24—27 are shared between ports 12 and 13.
s Queues 28—31 are shared between ports 14 and 15.
s Queues 32—35 are shared between ports 16 and 17.
s Queues 36—39 are shared between ports 18 and 19.
s Queues 40—43 are shared between ports 20 and 21.
s Queues 44—47 are shared between ports 22 and 23.
s Queues 48—51 are shared between ports 24 and 25.
s Queues 52—55 are shared between ports 26 and 27.
s Queues 56—59 are shared between ports 28 and 29.
s Queues 60—63 are shared between ports 30 and 31.
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