RDC
®
RISC DSP Controller
R8810LV
RDC Semiconductor Co.
Rev:1.2
Subject to change without notice
50
DMA Unit
The DMA controller provides the data transfer between the memory and peripherals without the intervention of the CPU.
There are two DMA channels in the DMA unit. Each channel can accept DMA request from one of two source :
external pin (DRQ0 for channel 0 or DRQ1 for channel 1) or Timer 2 overflow. The data transfer from source to destination
can be memory to memory or memory, to I/O, or I/O to I/O, or I/O to memory. Either bytes or words can be transferred to or
from even or odd addresses and two bus cycles are necessary (read from source and write to destination) for each data transfer.
DMA Operation
Every DMA transfer consists of two bus cycles (figure of Typical DMA Transfer) and the two bus cycles can not be separated
by a bus hold request, a refresh request or another DMA request. The registers ( CAh, C8h, C6h, C4h, C2h, C0h, DAh, D8h,
D6h, D4h, D2h, D0h) are used to configure and operate the two DMA channels.
DMA
Control
Logic
Adder Control
Logic
20-bit Adder/Subtractor
C8h-Transfer Counter Channel 0
C6h,C4h-Destination Address Channel 0
C2h,C0h-Source Address Channel 0
D8h-Transfer Counter Channel 1
D6h,D4h-Destination Address Channel 1
D2h,D0h-Source Address Channel 1
Request
Arbitration
Logic
INT
Interrupt Request
CAh.8-Channel 0
CAh.8-Channel 1
Channel Control Register1,DAh
Channel Control Register0,CAh
Internal Address/Data Bus
Timer 2 Request
DRQ0
DRQ1
TDRQ
CAH.4-Channel 0
DAH.4-Channel 1
20 bit
20 bit
16 bit
DMA Unit Block