MPC8280 datasheet(670/1386 Pages) FREESCALE

670 / 1386 page

SDMA Channels and IDMA Emulation

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

19-24

Freescale Semiconductor

Table 19-10 describes IDMA BD fields.

Table 19-10. IDMA BD Field Descriptions

Offset

Bits

Name

Description

0x00

Valid

0 This BD does not contain valid data for transfer.

1 This BD contain valid data for transfer.

The CP checks this bit before starting a BD service. If this bit is cleared when the CP

accesses the BD, an interrupt IDSR[OB] is issued to the core, the IDMA channel is

stopped until a START_IDMA command is issued. After the BD is serviced this bit is

cleared by CP unless CM = 1.

—

Reserved, should be cleared.

Wrap (final BD in table)

0 This is not the last BD in the BD table.

1 Last BD in the table. After the associated buffer has been used, the CP transfers data

from the first BD in the table, which is pointed by IBASE. The number of BDs in this

table is programmable and determined by W bit and the overall space constraints of

the dual-port RAM.

Interrupt

0 No interrupt is generated after this buffer is serviced.

1 When the CP services all the buffer’s data, IDSR[BC] is set, which generates a

maskable interrupt.

Last

0 Not the last buffer of a chain to be transferred in buffer chaining mode. The I bit can

be used to generate an interrupt when this buffer service is complete.

1 Last buffer of a chain to be transferred in buffer chaining mode. When this BD service

is complete the channel is stopped by CP until START_IDMA command is issued.

This bit should be set only in buffer chaining mode (CM bit 6 = 0).

—

Reserved, should be cleared.

Continuous mode

0 Buffer chaining mode. The CP clears V after this BD is serviced. Buffer chaining

mode is used to transfer large quantities of data into non-contiguous buffer areas.

The user can initialize BDs ahead of time, if needed. The CP automatically loads the

IDMA registers from the next BD values when the transfer is terminated.

1 Auto buffer mode (continuous mode). The CP does not clear V after this BD is

serviced. This is the only difference between auto buffer mode and buffer chaining

mode. Auto buffer mode transfers multiple groups of data to/from a buffer table and

does not require BD reprogramming. The CP automatically reloads the IDMA

registers from the next BD values when the transfer is terminated. Either a single BD

or multiple BDs can be used to create an infinite loop of repeated data moves.

Note: The I bit can still be used to generate an interrupt in this mode.

7-8

—

Reserved, should be cleared.

SDN

Source done

0DONE is inactive during this BD.

1 The IDMA asserts DONE at the last read data phase of the BD.

In fly-by mode (DCM[FB] = 1), SDN should be same as DDN.

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