MPC8280 datasheet(900/1386 Pages) FREESCALE

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Multi-Channel Controllers (MCCs)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

29-10

Freescale Semiconductor

29.3.1.4

Internal Receiver State (RSTATE)—HDLC Mode

Internal receiver state (RSTATE) is a 4-byte register that provides transaction parameters associated with

SDMA channel accesses (like function code registers) and starts the receiver channel.

To start the channel the user must write 0xHH800000 to RSTATE, where HH is the RSTATE high byte

(see Figure 29-5). When the channel is active the CP changes the value of the 3 LSBs, hence these 3 bytes

must be masked if the user reads back the RSTATE.

RSTATE high-byte fields are described in Table 29-5.

01234567

Field

—

GBL

TC2

DTB

BDB

Reset

—

R/W

Addr

0x20

Figure 29-5. Rx Internal State (RSTATE) High Byte

Table 29-5. RSTATE High-Byte Field Descriptions

Bits

Name

Description

0–1

—

Reserved, should be cleared.

GBL

Global. Setting GBL activates snooping (only the 60x bus can be snooped, this parameter is ignored

for local bus transactions).

3–4

Byte ordering. Set BO to select the required byte ordering for the buffer. If BO is changed on-the-fly,

it takes effect at the beginning of the next frame or at the beginning of the next BD.

00 Reserved

01 Munged little-endian.

1x Big-endian

TC2

Transfer code. Contains the transfer code value of TC[2], used during this SDMA channel memory

access. TC[0–1] is driven with a 0b11 to identify this SDMA channel access as a DMA-type access.

DTB

Data bus indicator.

The transfers to data buffers are handled by the:

0 60x bus SDMA

1 Local bus SDMA

BDB

BD and interrupt circular tables bus indicator.

The transfers to/from BD and interrupt circular tables are handled by the:

0 60x bus SDMA

1 Local bus SDMA

Note: The following restrictions result from the fact that there is a common bus selection bit for BDs

and interrupt circular tables:

• The RxBDs of all the channels that use a particular interrupt table must reside on the same bus

(60x or local).

• All TxBDs must reside on the same bus (60x or local).

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