CS4210 datasheet(19/102 Pages) NSC

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Operational Description (Continued)

3.3

COMMON DMA CONTROLLER FEATURES

The CS4210 provides several types of DMA functionality:

• General-purpose DMA handling asynchronous transmit

and receive packets and isochronous transmit and

receive packets.

• An inbound bus bridge function that allows 1394 devices

to directly access system memory called “physical

DMA.”

• A separate write buffer for the received Self-ID packets.

• Amapping betweena1KBblock in systemmemoryand

the first 1K of configuration ROM.

3.3.1

Context Registers

A context provides the basic information to the CS4210 to

allow it to fetch and process descriptors for one of the sev-

eral DMA controllers. All contexts (except for Self-ID) have

a ContextControl register and a CommandPtr register. The

format of the ContextControl Registers is DMA controller

specific.

Table 3-6 is a register format of the Contex.Control and

CommandPtr registers. Refer to Section 4.4.24 starting on

page 80 through Section 4.4.27 for further register informa-

tion.

3.3.2

ContextControl.event

Thepacketevent codesshowninTable 3-7onpage20are

possible values for the five-bit ContextControl.event field.

This field may contain either a 1394 defined ack code or an

OpenHCI generated event code. Bits [15:0] of the Context-

Control register may be written into host memory to indi-

cate packet and/or DMA descriptor status. However, all

possible event codes which may appear in a particular con-

text’s ContextControl register may not necessarily ever be

written into host memory for a packet or DMA descriptor

status, depending on circumstances and the functionality of

the context. The list of ack codes provided in Table 3-7 is

informative not normative (i.e., for asynchronous packets

the event code may be set to any ack code specified in cur-

rent and future 1394 standards). OpenHCI generated event

codes have an “evt_” prefix and are denoted by a code with

the high (fifth) bit equal to 0. In some cases for isochronous

I/O OpenHCI may generate a 1394 style ack code for Con-

textControl.event.

Table 3-6. ContextControl and CommandPtr Registers Formats

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

AsyncReqTxContextControl Set/Clear Registers

AsyncRespTxContextControl Set/Clear Registers

RSVD

event code

AsyncReqRxContextControl Set/Clear Registers

AsyncRespRxContextControl Set/Clear Registers

RSVD

spd

event code

IsochTxnContextControl Set/Clear Registers

cycleMatch

RSVD

event code

IsochRxnContextControl Set/Clear Registers

RSVD

spd

event code

CommandPtr Register

descriptorAddress

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