MPC8280 datasheet(1051/1386 Pages) FREESCALE

1051 / 1386 page

ATM Controller and AAL0, AAL1, and AAL5

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

31-91

31.15.1 FCC Transmit Internal Rate Mode

In internal rate mode the total transmission rate is the sum of the rates assigned for all PHYs. This register

controls how internal rate is configured. In internal rate mode (GFEMR[TIREM] = 0), the internal rate

assigned per PHY is configured by registers FTIRR[0-3]. In internal rate expanded mode

(GFEMR[TIREM] = 1), registers FTIRR[0-3] control the available rates, but the PHY settings are

configured in registers FIRPER, FIRSR_HI and FIRSR_LO. In TIREM = 0 mode internal rate can only

be used for PHYs[0-3], whereas in TIREM = 1 mode up to 31 PHYs are supported. If TIREM = 1 mode

is selected, the transmit internal rate underrun (TIRU) status per PHY may be read at any time in register

FIRER.

31.15.1.1 FCC Transmit Internal Rate Register (FTIRR

NOTE

The source clock of the internal rate timers is the BRGs clock, which is

configured in CMXUAR (refer to Section 16.4.1, “CMX UTOPIA Address

half of the FCC Tx Clock of the UTOPIA interface.

If GFEMR[TIREM] = 0, the first four PHY devices (address 00– 03) on FCC1 and FCC2 have their own

transmit internal rate registers (FTIRRx_PHY0–FTIRRx_PHY3) for use in transmit internal rate mode. In

this mode, the total transmission rate is determined by FCC internal rate timers. As a master, the controller

only polls the PHY’s Clav status at the rate determined by the internal rate. As a slave, the controller

attempts to insert cells into the FIFO at the internal rate. The controller can handle a lag of up to seven cells

per PHY between the programmable and actual bus rate. When the cell count mismatch reaches seven,

TIRU event is reported, see Section 31.13.3, “ATM Event Register (FCCE)/Mask Register (FCCM)”.

Note that a mismatch occurs if the PHY rate or the CPM performance are lower then the internal rate.

If GFEMR[TIREM] = 1, FTIRRx are used as group timers and PHYs at addresses 0-30 are assigned to a

rate group by FIRSRx_HI and FIRSRx_LO.

FTIRRx, shown in Figure 31-62, includes the initial value of the internal rate timer. The source clock of

the internal rate timers is supplied by one of four baud-rate generators selected in CMXUAR; see

Section 16.4.1, “CMX UTOPIA Address Register (CMXUAR).” Note that in slave mode, FTIRRx_PHY0

is used regardless of the slave PHY address.

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