ST18952
7 DMA Controller
The DMA controller manages data transfer between memories and external peripherals and
has the following features:
• four independent DMA channels
• transfers on X / Y / I spaces (simultaneous transfers on X and Y spaces)
• cycle stealing operation:
• 3 cycles for a single data transfer (+1cycle for transfers on I space)
• (n+2) cycles for an n-data block transfer (+1cycle for transfers on I space)
• each channel has:
• 3 signals: request (DMARQ), acknowledge (DMACK), interrupt request (DIT)
• 4x16 bit registers for block transfer facilities
• fixed priority between the four channels (highest channel 0, lowest channel 3)
The DMA controller DMARQ0-3 inputs and DMACK0-3 outputs are available as primary
inputs, in the case of SIO inhibition. This is set by the DMAR register (see ”DMAR: DMA
management register” on page 44).
Figure 7.1 DMA controller
IA ID XA XD
AS-D SP
16
YD
YA
16
16 16 16 16
D950Core
DMA_CLK
YRD
YWR
YBS
3
INTERR UPT
CONTROLLER
PERIPHERAL
HOLD HOLDACK CLK INCY CLE
DIT0 DIT1 DIT2 DIT3 DIT_AND
IRD
IWR
3
IBS
XR D
XW R
3
XB S
DMA CONTROLLER PERIPHERAL
RE SET
DMARQ0
DMARQ1
DMARQ2
DMARQ3
DM ACK0
DM ACK1
DM ACK2
DM ACK3
DTACK
DIP_ENA
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