82374EB datasheet(53/208 Pages) INTEL

53 / 208 page

82374EB82374SB

consists of two logical channel groups – Channels 0-3 (Controller 1-DMA1) and Channels 4-7 (Controller 2-

DMA2) Both groups may be assigned fixed priority one group can be assigned fixed priority and the second

rotating priority or both groups may be assigned rotating priority A detailed description of the channel priority

scheme is found in the DMA functional description Section 65 Following a reset or DMA Master Clear both

DMA-1 and DMA-2 are enabled in fixed priority the DREQ sense level is active high and the DACK

assertion level is active low

Bit

Description

DACK

Assert Level

Bit 7 controls the DMA channel request acknowledge (DACK ) assertion

level Following reset the DACK

assertion level is active low The low level indicates recognition and

acknowledgment of the DMA request to the DMA slave requesting service Writinga0tobit7 assigns

active low as the assertion level Whena1is written to this bit a high level on the DACK

line

indicates acknowledgment of the request for DMA service to the DMA slave

DREQ Sense Assert Level

Bit 6 controls the DMA channel request (DREQ) assertion detect level

Following reset the DREQ sense assert level is active high In this condition an active high level

sampled on DREQ is decoded as an active DMA channel request Writinga0tobit6 assigns active

high as the sense assert level Whena1is written to this bit a low level on the DREQ line is decoded

as an active DMA channel request

Reserved

Must be 0

DMA Group Arbitration

Each channel group is individually assigned either fixed or rotating arbitration

priority At reset each group is initialized in fixed priority Writinga0tobit4 assigns fixed priority to the

channel group while writing a 1 assigns rotating priority to the group

Reserved

Must be 0

DMA Group Enable

Writinga1to this bit disables the DMA channel group while writinga0to this bit

enables the DMA channel group Both channel groups are enabled following reset Disabling Channel

group 4-7 also disables Channel group 0-3 which is cascaded through Channel 4

Reserved

Must be 0

82374EB Folha de dados(PDF) 53 Page - Intel Corporation