82374EB Datasheet, PDF (53/208 Pages) Intel Corporation – SYSTEM COMPONENT (ESC)

82374EB 82374SB
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 6 5 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
7 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 Writing a 0 to bit 7 assigns
active low as the assertion level When a 1 is written to this bit a high level on the DACK line
indicates acknowledgment of the request for DMA service to the DMA slave
6 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 Writing a 0 to bit 6 assigns active
high as the sense assert level When a 1 is written to this bit a low level on the DREQ line is decoded
as an active DMA channel request
5 Reserved Must be 0
4 DMA Group Arbitration Each channel group is individually assigned either fixed or rotating arbitration
priority At reset each group is initialized in fixed priority Writing a 0 to bit 4 assigns fixed priority to the
channel group while writing a 1 assigns rotating priority to the group
3 Reserved Must be 0
2 DMA Group Enable Writing a 1 to this bit disables the DMA channel group while writing a 0 to 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
1 0 Reserved Must be 0
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