A8237 datasheet(21/22 Pages) ALTERA

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Altera Corporation

a8237 Programmable DMA Controller Data Sheet

The a8237 does not support the cascade mode because it would not

be an efficient use of device resources. To implement this capability,

the designer should use a hand-coded module or a stripped down

a8237

function.

On the rising edge of CLK, the Harris 82C37A deasserts nMEMR on

states 4 and 14, and deasserts nIOROUT on state 4. However, this

approach is not reliable from a timing perspective for a CPLD.

The Altera a8237 deasserts nMEMR on the falling edge of CLK at the

end of states 4 and 14 and nIOROUT at the end of state 4. This action

effectively extends the assertion of these signals by a 1/2 clock cycle.

Revision

History

The information contained in the a8237 Programmable DMA Controller Data

Sheet version 1.01 supersedes information published in previous versions.

Version 1.01 includes the following changes:

The “State Machine” on page 18 was updated.

The waveforms in Figures 2 and 3 were updated.

The “Variations & Clarifications” on page 24 was updated.

Minor style and text changes were made throughout the document.

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