Confidential Draft
3/7/00
CS4281 Programming Manual
122
DS308PRM1
13.3.6
I/O Trap CCLS Control Register (IOTCC)
Address:
BA0: 530h, Read-Write
Default:
00000000h
Definition: Provides I/O Trapping control for CCLS legacy 8237 trapping when enabled
(
IOTCR.EDMA[1:0]
= 01). When any
C1xxx or C2xxx
bit is set, write snooping to 0Ch is
enabled. Once enabled, any write to 0Ch clears
BPFF
. There is no initialization
associated with setting bits in this register; therefore, this register can be dynamically managed by
software wanting access to the real legacy DMA controller.
Bit Descriptions:
C1RE
CCLS 1 Read Enable: When set, read trapping is enabled for the CCLS assigned legacy
DMAn controller (
IOTCR.DMA
) Current Address, Current Count, and Address Page registers.
When
C1RE
is set,
BPFF
is toggled on every read and write access to the Base/Current Count
and Base/Current Address DMA registers (not the Address Page register).
0 = Read trapping disabled (reset default)
1 = Read trapping enabled
C1WE
CCLS 1 Write Enable: When set, write trapping is enabled for the CCLS assigned legacy
DMAn controller (
IOTCR.DMA
) Base Address, Base Count, and Address Page registers. This
bit is mutually exclusive with
C1WSE
. When
C1WE
is set,
BPFF
is toggled on every read and
write access to the Base/Current Count and Base/Current Address DMA registers (not the
Address Page register).
0 = Write trapping disabled (reset default)
1 = Write trapping enabled
C1WSE
CCLS 1 Write Snoop Enable: When set, the CCLS I/O Trap logic snoops the writes to the
CCLS-assigned legacy DMAn controller (
IOTCR.DMA
) Base Address, Base Count, and
Address Page registers. Instead of claiming the I/O write transaction, the CS4281 captures
data written to the snooped I/O range and stores it in the appropriate register, just as if the I/O
location was actually trapped. The actual legacy 8237 will claim these transactions. This bit is
mutually exclusive with
C1WE
. When
C1WE
is set,
BPFF
is toggled on every read and write
access to the Base/Current Count and Base/Current Address DMA registers (not the Address
Page register).
0 = Write snooping disabled (reset default)
1 = Write snooping enabled
C2WSE
CCLS 2 Write Snoop Enable: When set, the CCLS I/O Trap logic snoops writes to the
addresses between 0 through 7 not claimed or snooped by
C1xxx
bits.
When a write occurs to these registers,
BPFF
is XOR’d.
C2RSE
CCLS 2 Read Snoop Enable: When set, the CCLS I/O Trap logic snoops reads to the addresses
between 0 through 7 not claimed by
C1RE
. When a read occurs to these
registers,
BPFF
is XOR’d.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
C1RE
C1WE
C1WSE
C2WSE
C2RSE
BPFF
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
C3WSE
C4RE
C4WSE
D
ra
ft
Содержание CS4281
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