CS4281 Programming Manual
DS308PRM1
117
Confidential Draft
3/7/00
13.3.1
I/O Trap Game Port (IOTGP)
Address:
BA0: 500h, Read-Write
Default:
00000000h
Definition: Trapping I/O for the Game port. All trapped addresses are channeled to one internal register, JSPT
(BA0:480h).
Bit Descriptions:
SA[15:0]
GameBase Start Address: Starting PCI I/O space address of the trap range. Bits above the I/O
Decode Control bits must be set to 0. For example, if
IODC[1:0]
= 10,
SA15-SA10
must be 0.
MSK[2:0] Address Mask: Logically, these bits are used to selectively mask off the lower four bits of
address accompanying an I/O transaction. After the mask operation is performed, the resulting
address is compared against SA[15:0]; if they are equal, the original I/O transaction lies within
the trap range. The cycle is trapped and connected to register JSPT.
DLY[3:0]
Delay PCI Cycle for this number of PCICLKs. TRDY# is delayed this number of clocks on
both read and write transactions. The
DLY
number does not include the normal clocks required
by the bus interface logic. For example, if the but interface logic normally takes 5 PCICLKs to
complete the transaction and
DLY[3:0]
= 3, then the entire PCI cycle will take 8 cycles. Up to
15 clocks can be added.
IODC[1:0] I/O Decode Control: These two bits control how many I/O address bits are decoded for the
trap range.
0 0 = Decode
SA15
down to
MSK
bits of I/O address (no aliasing, reset default)
0 1 = Decode
SA11
down to
MSK
bits of I/O address (
SA15-SA12
alias)
1 0 = Decode
SA9
down to
MSK
bits of I/O address (
SA15-SA10
alias)
1 1 = Reserved
WE
Write Enable: This bit controls whether or not write trapping is enabled for the trap range.
0 = Write trapping disabled (reset default)
1 = Write trapping enabled
RE
Read Enable: This bit controls whether or not read trapping is enabled for the trap range.
0 = Read trapping disabled (reset default)
1 = Read trapping enabled
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RE
WE
res
res
res
IODC1
IODC0
DLY3
DLY2
DLY1
DLY0
MSK2
MSK1
MSK0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SA15
SA14
SA13
SA12
SA11
SA10
SA9
SA8
SA7
SA6
SA5
SA4
SA3
SA2
SA1
SA0
D
ra
ft
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