CS4210 Datasheet, PDF (19/102 Pages) National Semiconductor (TI) – IEEE 1394 OHCI Controller

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.
• A mapping between a 1 KB block in system memory and
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
The packet event codes shown in Table 3-7 on page 20 are
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 9 8 7 6 5 4 3 2 1 0
RSVD
AsyncReqTxContextControl Set/Clear Registers
AsyncRespTxContextControl Set/Clear Registers
RSVD
RSVD
event code
AsyncReqRxContextControl Set/Clear Registers
AsyncRespRxContextControl Set/Clear Registers
RSVD
RSVD
RSVD
spd
event code
IsochTxnContextControl Set/Clear Registers
cycleMatch
RSVD
RSVD
event code
IsochRxnContextControl Set/Clear Registers
RSVD
RSVD
RSVD
spd
event code
CommandPtr Register
descriptorAddress
Z
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