Analog Devices ADSP-2181 - Manual (Page 7)

ADSP-2181/ADSP-2183
REV. 0 –7–
Table II.
PMOVLAY Memory A13 A12:0
0 Internal Not Applicable Not Applicable
1 External 0 13 LSBs of Address
Overlay 1 Between 0x2000
and 0x3FFF
2 External 1 13 LSBs of Address
Overlay 2 Between 0x2000
and 0x3FFF
This organization provides for two external 8K overlay segments
using only the normal 14 address bits. This allows for simple
program overlays using one of the two external segments in
place of the on-chip memory. Care must be taken in using this
overlay space in that the processor core (i.e., the sequencer)
does not take into account the PMOVLAY register value. For
example, if a loop operation was occurring on one of the exter-
nal overlays and the program changes to another external over-
lay or internal memory, an incorrect loop operation could occur.
In addition, care must be taken in interrupt service routines as
the overlay registers are not automatically saved and restored on
the processor mode stack.
For ADSP-2100 Family compatibility, MMAP = 1 is allowed.
In this mode, booting is disabled and overlay memory is dis-
abled (PMOVLAY must be 0). Figure 5 shows the memory map
in this configuration.
INTERNAL 8K
(PMOVLAY = 0,
MMAP = 1)
0x3FFF
0x2000
0x1FFF
8K EXTERNAL
0x0000
PROGRAM MEMORY ADDRESS
Figure 5. Program Memory (MMAP = 1)
Data Memory
The ADSP-2181/ADSP-2183 has 16,352 16-bit words of inter-
nal data memory. In addition, the ADSP-2181/ADSP-2183
allows the use of 8K external memory overlays. Figure 6 shows
the organization of the data memory.
8K INTERNAL
(DMOVLAY = 0)
OR
EXTERNAL 8K
(DMOVLAY = 1, 2)
INTERNAL
8160 WORDS
DATA MEMORY ADDRESS
32 MEMORY–
MAPPED REGISTERS
0x3FFF
0x3FEO
0x3FDF
0x2000
0x1FFF
0x0000
Figure 6. Data Memory
Memory Architecture
The ADSP-2181/ADSP-2183 provides a variety of memory and
peripheral interface options. The key functional groups are Pro-
gram Memory, Data Memory, Byte Memory, and I/O.
Program Memory is a 24-bit-wide space for storing both in-
struction opcodes and data. The ADSP-2181/ADSP-2183 has
16K words of Program Memory RAM on chip, and the capabil-
ity of accessing up to two 8K external memory overlay spaces
using the external data bus. Both an instruction opcode and a
data value can be read from on-chip program memory in a
single cycle.
Data Memory is a 16-bit-wide space used for the storage of
data variables and for memory-mapped control registers. The
ADSP-2181/ADSP-2183 has 16K words on Data Memory RAM
on chip, consisting of 16,352 user-accessible locations and 32
memory-mapped registers. Support also exists for up to two 8K
external memory overlay spaces through the external data bus.
Byte Memory provides access to an 8-bit wide memory space
through the Byte DMA (BDMA) port. The Byte Memory inter-
face provides access to 4 MBytes of memory by utilizing eight
data lines as additional address lines. This gives the BDMA Port
an effective 22-bit address range. On power-up, the DSP can
automatically load bootstrap code from byte memory.
I/O Space allows access to 2048 locations of 16-bit-wide data.
It is intended to be used to communicate with parallel periph-
eral devices such as data converters and external registers or
latches.
Program Memory
The ADSP-2181/ADSP-2183 contains a 16K
×
24 on-chip
program RAM. The on-chip program memory is designed to al-
low up to two accesses each cycle so that all operations can
complete in a single cycle. In addition, the ADSP-2181/ADSP-
2183 allows the use of 8K external memory overlays.
The program memory space organization is controlled by the
MMAP pin and the PMOVLAY register. Normally, the ADSP-
2181/ADSP-2183 is configured with MMAP = 0 and program
memory organized as shown in Figure 4.
8K INTERNAL
(PMOVLAY = 0,
MMAP = 0)
OR
EXTERNAL 8K
(PMOVLAY = 1 or 2,
MMAP = 0)
0x3FFF
0x2000
0x1FFF
8K INTERNAL
0x0000
PROGRAM MEMORY ADDRESS
Figure 4. Program Memory (MMAP = 0)
There are 16K words of memory accessible internally when the
PMOVLAY register is set to 0. When PMOVLAY is set to
something other than 0, external accesses occur at addresses
0x2000 through 0x3FFF. The external address is generated as
shown in Table II.