CS4210 Datasheet, PDF (17/102 Pages) National Semiconductor (TI) – IEEE 1394 OHCI Controller

Operational Description (Continued)
3.2.3.3 Isoch Tx and Rx Context Interrupts
Each of the eight implemented isochronous transmit and
each of the eight implemented isochronous receive con-
texts can generate an interrupt. Software can enable inter-
rupts on a per-context basis by setting the corresponding
IsochTxnContextIntMask or IsochRxnContextIntMask bit to
one. To efficiently handle interrupts which could conceiv-
ably be generated from eight different contexts in close
proximity to one another, there is a single bit for all IT DMA
contexts and another for all IR DMA contexts in the
CS4210 IntEvent register. These bits signify that at least
one but potentially several IT or IR DMA contexts
attempted to generate an interrupt. Software can read the
isochTxIntEvent register to find out which isochronous
transmit context(s) are involved. Software can read the Iso-
chRxIntEvent register to find out which isochronous receive
context(s) are involved.
Table 3-4 shows a map of the IsochTx/Rx Context Interrupt
Event and Mask Set/Clear registers. Refer to Section
4.4.16.4 on page 73 through Section 4.4.16.7 on page 74
for further register information.
The number of supported isochronous DMA contexts var-
ies for 1394 OHCI implementations from a minimum of four
to a maximum of 32. Software can determine the number
of supported IT or IR DMA contexts by writing
FFFF_FFFFh to IsochTxIntMask register for IT and Isoch-
RxIntMask register for IR, and then reading it back. Bits
returned as 1’s indicate supported contexts, and bits
returned as 0’s indicate unsupported/unimplemented con-
texts.
Table 3-4. IsochTx and IsochRx Context Interrupt Related Registers
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
BAR0+Offset 90h
BAR0+Offset 94h
IsochTxIntEvent Set Register
IsochTxIntEvent Clear Register
RSVD
BAR0+Offset 98h
BAR0+Offset 9Ch
IsochTxIntMask Set Register
IsochTxIntMask Clear Register
RSVD
BAR0+Offset A0h
BAR0+Offset A4h
BAR0+Offset A8h
BAR0+Offset ACh
IsochRxIntEvent Set Register
IsochRxIntEvent Clear Register
RSVD
IsochRxIntMaskSet Register
IsochRxIntMaskClear Register
RSVD
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