Analog Devices adsp-2100 Manual page 244

includes four fields for the ADSP-2181's I/O memory space.
The Data Memory overlay select (DMOVLAY) register lets you choose a
memory overlay to map from address DM(0x0000) to address DM(0x1FFF).
The DMOVLAY register is unique to the ADSP-2181. The memory mapped
to this space and corresponding DMOVLAY contents are shown in Figure
10.29. Table 10.4 shows how DMOVLAY relates to memory addressing
(address line A13).
DMOVLAY Memory
0 Internal
1 External overlay 1
2 External overlay 2
Table 10.4 DMOVLAY and Data Memory Overlay Addressing
The following example instructions demonstrate how to use the DMOVLAY
register:
DMOVLAY=DM(0x1234);
}
DM(0x1234)}
DMOVLAY=2;
DMOVLAY=AX0;
AX0=DMOVLAY;
For an example memory design that provides full external program and
data memory overlays for an ADSP-2181 processor, see the previous section
"Program Memory Interface."
Two control lines indicate the direction of external transfers. Memory read
RD
( ) is active low signaling a read and memory write (
a write operation. Typically, you would connect
Memory Interface
A13 A12:0
— —
0 13 LSBs of address between
0x0000 and 0x1FFF
1 13 LSBs of address between
0x0000 and 0x1FFF
{type 3 instruction, DMOVLAY is loaded
{ with the contents of address
{type 7 instruction, DMOVLAY is loaded }
{ with the value 2. }
{DMOVLAY is loaded from AX0 register.}
{AX0 is loaded from DMOVLAY register.}
WR
) is active low for
DMS CE
to (Chip Enable),
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