Lattice Semiconductor
Multi-Channel DMA Controller User’s Guide
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Demand Transfer Mode:
In demand transfer mode, the device is programmed to continue making transfers until
a Terminal Count or external
eopin_n
is encountered or until
dreq
goes inactive. Thus, transfers continue until
the I/O device has exhausted its data capacity. After the I/O device has had a chance to catch up, the DMA ser-
vice is reestablished by
dreq
.
Parameter Descriptions
Table 3 lists the parameters used to configure the MCDMA core. The values of these parameters must be set prior
to functional verification. The parameters in parenthesis can be configured using the IPexpress™ software tool,
included with the ispLEVER
®
design tools.
Table 3. MCDMA Parameters
Parameter
Description
Supported Values
DMA Mode (MODE_8237)
Defines the DMA mode. If it is TRUE, the DMA will be in
8237 mode, otherwise it will be in non-8237 mode.
TRUE/FALSE
Number of Channel
(NUM_CHANNELS)
Sets the number of channels. In 8237 mode it is fixed to 4
channels. In non 8237 it can be set for 1 to 16 channels
4 (8237)
1-16 (non 8237)
Data Width
(DATA_BUS_WIDTH)
Sets the size of data buses and the temporary register.
8 (8237)
8/16/32/64 (non 8237)
Address Width
(ADDR_BUS_WIDTH)
Sets the size of DMA output address. In the 8237 mode, it
sets the size of the current and base address register. In the
non-8237 mode, it sets the size of the source address regis-
ter
16 (8237)
16/24/32 (non 8237)
Word Count Width
(WORD_COUNT_WIDTH)
Sets the size of the Word Count Register.
16 (8237)
8/16/24/32 (non 8237)
Internal Address Width
(AIN_BUS_WIDTH)
Value is set automatically based in the number of channels
parameter (NUM_CHANNELS or N).
4 (8237)
3 when N = 1 (non 8237)
4 when N = 2 (non 8237)
5 when 3
≤
N
≤
4 (non 8237)
6 when 5
≤
N
≤
8 (non 8237)
7 when 9
≤
N
≤
16 (non 8237)