adsp-21mod870-100 Analog Devices, Inc., adsp-21mod870-100 Datasheet - Page 9

• Manufacturer Part Number: adsp-21mod870-100
• Description: Internet Gateway Processor
• Manufacturer: Analog Devices, Inc.

held at a constant level and will not oscillate if the three-state
driver’s level hovers around the logic switching point.
MEMORY ARCHITECTURE
The ADSP-21mod870 provides a variety of memory and pe-
ripheral interface options. The key functional groups are Pro-
gram Memory, Data Memory, Byte Memory and I/O. Refer to
the following figures and tables for PM and DM memory alloca-
tions in the ADSP-21mod870.
Program Memory
The Program Memory map is shown in Figure 5.
Program Memory (Full Memory Mode) is a 24-bit space for
storing both instruction op codes and data. The ADSP-21mod870
has 32K words of Program Memory RAM on chip, and the
capability of accessing up to two 8K external memory overlay
spaces using the external data bus.
REV. 0
INTERNAL
MEMORY
PROGRAM MEMORY
ACCESSIBLE WHEN
PMOVLAY = 0, 4, 5
INTERNAL
MEMORY
PMOVLAY = 1, 2
0x0000 – 0x1FFF
EXTERNAL
MEMORY
8K EXTERNAL
8K INTERNAL
8K INTERNAL
PMOVLAY = 0
PM MODE B=0
ACCESSIBLE
AT ADDRESS
MODE B = 0
ACCESSIBLE WHEN
PMOVLAY = 4
ALWAYS
OR
ACCESSIBLE WHEN
PMOVLAY = 5
ACCESSIBLE WHEN
DATA MEMORY
0x2000 – 0x3FFF
EXTERNAL
MEMORY
DMOVLAY = 0
ACCESSIBLE
AT ADDRESS
ACCESSIBLE WHEN
DMOVLAY = 4
ACCESSIBLE WHEN
PMOVLAY = 1
ALWAYS
ACCESSIBLE WHEN
DMOVLAY = 5
ACCESSIBLE WHEN
PMOVLAY = 2
ADDRESS
0x2000–
0x3FFF
0x3FFF
0x2000
0x1FFF
0x0000
ACCESSIBLE WHEN
DMOVLAY = 1
Figure 6. Data Memory Map
Figure 5. Program Memory
0x2000–
0x3FFF
ACCESSIBLE WHEN
DMOVLAY = 2
0x2000–
0x1FFF
0x2000–
0x3FFF
0x0000–
0x1FFF
0x2000–
0x3FFF
0x0000–
0x1FFF
0x2000–
0x3FFF
2
–9–
INTERNAL
MEMORY
0x0000–
0x1FFF
2
Program Memory (Host Mode) allows access to all internal
memory. External overlay access is limited by a single external
address line (A0). External program execution is not available in
host mode due to a restricted data bus that is 16 bits wide only.
The PMOVLAY bits are defined in Table III.
0x0000–
0x1FFF
PMOVLAY
0, 4, 5
1
2
Data Memory
The Data Memory map is shown in Figure 6.
PROGRAM MEMORY
ACCESSIBLE WHEN
PMOVLAY = 0
1
2
PM (MODE B=1)
EXTERNAL
MEMORY
WHEN MODE = 1, PMOVLAY MUST BE SET TO 0
SEE TABLE III FOR PMOVLAY BITS
8K EXTERNAL
8K INTERNAL
PMOVLAY = 0
MODE B = 1
RESERVED
DMOVLAY = 0, 4, 5
DATA MEMORY
DMOVLAY = 1, 2
RESERVED
EXTERNAL 8K
32 MEMORY
REGISTERS
8K INTERNAL
INTERNAL
MAPPED
WORDS
ACCESSIBLE WHEN
PMOVLAY = 1
RESERVED
8160
OR
1
Memory
Internal
External
Overlay 1
External
Overlay 2
ADDRESS
0x2000–
0x3FFF
0x3FFF
0x1FFF
0x0000
Table III. PMOVLAY Bits
0x2000
RESERVED
ADDRESS
0x3FFF
0x3FE0
0x3FDF
0x1FFF
0x2000
0x0000
Not Applicable
0
1
A13
1
0x0000–
0x1FFF
ADSP-21mod870
2
A12:0
Not Applicable
13 LSBs of Address
Between 0x2000
and 0x3FFF
13 LSBs of Address
Between 0x2000
and 0x3FFF