Programming The Mcdma Controller; Reference Information; Technical Support Assistance - Lattice Semiconductor ispLever Core Multi-Channel DMA Controller User Manual

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Programming the MCDMA Controller

Programming the core to achieve the desired functionality is very similar in both the 8237 and non-8237 modes.
The differences lie in the address map and the name of the registers
For the 8237 mode, the steps to program the core are:
• Disable the controller through the command register
• Program the Mode Register
– Select the channel to be programmed
– Set the features on the channel to programmed, such as transfer mode, read/write/verify transfer, address
increment/decrement, etc.
• Write into the Address Registers and Word Count Register
– Set the base source address register
– Set the number of transfer to be performed in the Word Count Registers.
• Enable the controller
For the non-8237 mode, the steps to program the core are:
• Disable the controller
• Set Input ain
– The first 3 bits of ain, ain[2:0], selects which registered to be programmed. The rest of the bits select
which channel to be programmed.
• Program the Mode and Channel control registers of all the channels
• Write into the Address registers and Word Count register
• Enable the controller
The core remains in the idle state (SI) as long as DMA transfers are not requested. While in state SI, the dreq sig-
nals are sampled. When an unmasked DMA request is presented, the core enters the active state. The request can
be either a software or hardware request.
Although the internal registers can be programmed in state S0, or before the hlda signal is asserted, it is a good
practice to program the internal registers only while the core is in the Idle state (SI). The functionality of the control-
ler is not guaranteed to be deterministic if the internal registers are accessed during an active DMA cycle.

Reference Information

• ispLEVER Software User Manual, Lattice Semiconductor Corporation
• 8237A High Performance Programmable DMA Controller, Intel Corporation, September 1993.

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Multi-Channel DMA Controller User's Guide
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