RDC
®
RISC DSP Controller
R8810LV
RDC Semiconductor Co.
Rev:1.2
Subject to change without notice
55
Bit 15-4
: Reserved
Bit 3-0: DSA19-DSA16
, High DMA 1 Source Address. These bits are mapped to A19- A16 during a DMA transfer when the
source address is in memory space or I/O space. If the source address is in I/O space (64Kbytes), these bits must be
programmed to 0000b.
Bit 15-0: DSA15-DSA0
, Low DMA 1 Source Address. These bits are map to A15- A0 during a DMA transfer.
The value of (DSA19-DSA0)b will increment or decrement by 2 after each DMA transfer.
External Requests
External DMA requests are asserted on the DRQ pins. The DRQ pins are sampled on the falling edge of CLKOUTA. It takes a
minimum of four clocks before the DMA cycle is initiated by the Bus Interface. The DMA request is cleared four clocks
before the end of the DMA cycle. And no DMA acknowledge is provided, since the chip-selects (MCSx, PCSx) can be
programmed to be active for a given block of memory or I/O space, and the DMA source and destination address registers can
be programmed to point to the same given block.
DMA transfer can be either source or destination synchronized, and it can also be unsynchronized. The Source-Synchronized
Transfer figure shows the typical source-synchronized transfer which provides the source device at least three clock cycles
from the time it is acknowledged to deassert its DRQ line.
DMA Source Address Low Register
Offset : D0h (DMA1)
0
Reset Value :
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
DSA15 - DSA0
DMA Source Address High Register
Offset : D2h (DMA1)
0
Reset Value :
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
DSA19 - DSA16
Reserved