CS4210 datasheet(27/102 Pages) NSC

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Operational Description (Continued)

3.6.2

Posted Writes

For write requests handled by the Physical Request con-

troller, the CS4210 may send an ack_complete before the

data is actually written to system memory. These writes are

referred to as posted writes since posted writes impact the

Physical Request controller and the Asynchronous Receive

Request DMA context. Further information about posted

writes is located in Section 3.5.3 "Posted Writes" on page

24. Information on host bus error handling of posted writes

is provided in Section 3.7.7 "Posted Write Error" on page

29.”

3.6.3

Physical Responses

The response packet generated for a physical read, non-

posted write, and lock request contains the transaction

label as it appeared in the request, the destination_ID as

provided in the request’s source_ID, and are transmitted at

the speed at which the request was received. The source

bus ID in the response packet is equal to the destination

bus ID from the original request. Note that this is not neces-

sarily the same as the contents of the busNumber field in

the Node ID register (BAR0+Offset E8h[15:6]). Unlike AR

Response packets, physical responses do not track a

SPLIT_TIMEOUT expiration time.

3.6.4

Physical Response Retries

There is a separate nibble-wide MaxPhysRespRetries field

in the ATRetries Register (BAR0+Offset 08h[15:11]) that

tells the Physical Response Unit how many times to

attempt to retry the transmit operation for the response

packet when an ack_busy* or ack_data_error is received

from the target node. If the retry count expires, the packet

is dropped and software is not notified. Refer to Section

4.4.3 "ATRetries Register" on page 59 for register details.

3.6.5

Interrupt Considerations for Physical Requests

Physical read request handling does not cause an interrupt

to be generated under any circumstances. Physical write

requests generate an interrupt when posted write process-

ing yields an error. Lock requests to the serial bus registers

generate an interrupt when the CS4210 is unable to deliver

a lock response packet.

3.6.6

Bus Reset

On a bus reset, all pending physical requests (those for

which ack_pending was sent) are discarded. Following a

bus reset, only physical requests to the autonomous CSR

resources

(see

Section

4.4.4

"Autonomous

CSR

Resources" on page 60) can be handled immediately.

Other physical requests are processed after software ini-

tializes the filter registers (see Section 4.4.22 "Asynchro-

nous Request Filter Registers" on page 78 and Section

4.4.23 "Physical Request Filter Registers" on page 79).

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