MPC8280 datasheet(1173/1386 Pages) FREESCALE

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Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

34-27

34.4.4.1.1

IMA Group Transmit Control (IGTCNTL)

The fields of the IGTCNTL register are shown in Figure 34-14.

Table 34-6 describes the IGTCNTL bit fields.

1Ensure transmit clock mode is not changed during IMA group startup to avoid erratic behavior.

34.4.4.1.2

IMA Group Transmit State (IGTSTATE)

The fields of the IGTSTATE register are shown in Figure 34-15.

234567

Field

—

TXSC

ISIE

CTC

ICPC

Figure 34-14. IMA Group Transmit Control (IGTCNTL)

Table 34-6. IGTCNTL Field Descriptions

Bits

Name

Description

0–2

—

Reserved

3–4

TXSC

Transmit status/control. Sets the transmit mode of the IMA group.

00 Filler mode. The IMA group transmits only ICP and filler cells, no data cells.

01 Active mode. The IMA group is capable of sending data cells.

1X Reserved.

ISIE

Required for optional TRL Service Latency enhancement only.

IMA Scheduler Split Iterations Enable

0 - APC is not split, TRL completes round robin distribution of cells.

1 - APC split, both TRL and non-TRL requests distribute cells to the transmit queues.

6CTC1

Transmit clock mode for this IMA group.

0 Independent transmit clock (ITC) mode.

1 Common transmit clock (CTC) mode.

ICPC

ICP change flag. Maintains at least the minimum 2-frame spacing of ICP cell control/status

changes. Initialize to zero at group start-up.

Must be toggled by software whenever TICPPTR is changed.

After two subsequent IMA frames are transmitted, the IGTSTATE[ICPCA] field will be changed

to match IGTCNTL[ICPC]. When IGTCNTL[ICPC] equals IGTSTATE[ICPCA], changes to

TICPPTR are allowed.

01234567

Field

TSTF

TIMSTf

GTE

TRQS

ELX

—

ICH

ICPCA

Figure 34-15. IMA Group Transmit State (IGTSTATE)

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