SECTION 4
PCI 9080
REGISTERS
PLX Technology, Inc., 1997
Page 78
Version 1.02
4.6 DMA REGISTERS
4.6.1 (DMAMODE0; PCI:80h, LOC:100h) DMA Channel 0 Mode Register
Table 4-62. (DMAMODE0; PCI:80h, LOC:100h) DMA Channel 0 Mode Register
Field
Description
Read
Write
Value after Reset
1:0
Local Bus Width. Value of 00 indicates bus width of 8 bits, a value of 01 indicates
bus width of 16 bits and a value of 10 or 11 indicates bus width of 32 bits.
Yes
Yes
S = 01
J = 11
C = 11
5:2
Internal Wait States (data to data).
Yes
Yes
0
6
Ready Input Enable. Value of 1 enables Ready input. Value of 0 disables Ready
input.
Yes
Yes
0
7
BTERM# Input Enable. Value of 1 enables BTERM# input. Value of 0 disables
BTERM# input. If this bit is set to 0, PCI 9080 bursts four Lword maximum at a time.
Yes
Yes
0
8
Local Burst Enable. Value of 1 enables bursting. Value of 0 disables local bursting.
If burst is disabled, the local bus performs continuous single cycles for burst PCI
read/write cycles.
Yes
Yes
0
9
Chaining. Value of 1 indicates chaining mode is enabled. For chaining mode, the
DMA source address, destination address and byte count are loaded from memory
in PCI or Local Address Spaces. Value of 0 indicates nonchaining mode is enabled.
Yes
Yes
0
10
Done Interrupt Enable. Value of 1 enables interrupt when done. Value of 0 disables
interrupt when done. If DMA Clear Count mode is enabled, the interrupt won’t occur
until the byte count is cleared.
Yes
Yes
0
11
Local Addressing Mode. Value of 1 indicates local address LA[31:2] to be held
constant. Value of 0 indicates local address is incremented.
Yes
Yes
0
12
Demand Mode. Value of 1 causes DMA controller to operate in Demand mode. In
Demand mode, the DMA controller transfers data when its DREQ[1:0]# input is
asserted. It asserts DACK[1:0]# to indicate the current local bus transfer is in
response to the DREQ[1:0]# input. DMA controller transfers Lwords (32 bits) of
data. This may result in multiple transfers for an 8- or 16-bit bus.
Yes
Yes
0
13
Write and Invalidate Mode for DMA Transfers. When set to 1, PCI 9080 performs
Write and Invalidate cycles to the PCI bus. PCI 9080 supports Write and Invalidate
sizes of 8 or 16 Lwords. The size is specified in the PCI Cache Line Size Register.
If a size other than 8 or 16 is specified, PCI 9080 performs write transfers rather
than Write and Invalidate transfers. Transfers must start and end at the Cache Line
Boundaries.
Yes
Yes
0
14
DMA EOT (End of Transfer) Enable. Value of 1 enables EOT[1:0]# input pin. Value
of 0 disables EOT[1:0]# input pin. (Refer to Section 3.7.6.1, “End of Transfer
(EOT0# or EOT1#) Input.”)
Yes
Yes
0
15
DMA Stop Data Transfer Mode. Value of 0 sends a BLAST to terminate DMA
transfer. Value of 1 indicates an EOT asserted or DREQ[1:0]# negated during
demand mode DMA terminates the DMA transfer. (Refer to Section 3.7.6.1, “End of
Transfer (EOT0# or EOT1#) Input.”)
Yes
Yes
0
16
DMA Clear Count Mode. When set to 1, the byte count in each chaining descriptor,
if it is in local memory, is cleared when the corresponding DMA transfer is
complete.
Note:
If chaining descriptor is in PCI memory, the count is not cleared.
Yes
Yes
0
17
DMA Channel 0 Interrupt Select. Value of 1 routes the DMA Channel 0 interrupt to
the PCI interrupt. Value of 0 routes the DMA Channel 0 interrupt to the local bus
interrupt.
Yes
Yes
0
31:18
Reserved.
Yes
No
0