PIC18F87J10 Datasheet, PDF (60/394 Pages) Microchip Technology – 64/80-Pin High-Performance, 1-Mbit Flash Microcontrollers with nanoWatt Technology

PIC18F87J10 FAMILY
5.1.4
EXTENDED MICROCONTROLLER
MODE AND ADDRESS SHIFTING
By default, devices in Extended Microcontroller mode
directly present the program counter value on the
external address bus for those addresses in the range
of the external memory space. In practical terms, this
means addresses in the external memory device below
the top of on-chip memory are unavailable.
To avoid this, the Extended Microcontroller mode
implements an address shifting option to enable auto-
matic address translation. In this mode, addresses
presented on the external bus are shifted down by the
size of the on-chip program memory and are remapped
to start at 0000h. This allows the complete use of the
external memory device’s memory space.
FIGURE 5-3:
MEMORY MAPS FOR PIC18F87J10 FAMILY PROGRAM MEMORY MODES
Microcontroller Mode⁽¹⁾
Extended Microcontroller Mode⁽²⁾
Extended Microcontroller Mode
with Address Shifting⁽²⁾
On-Chip
Memory
Space
000000h
On-Chip
Program
Memory
(Top of Memory)
(Top of Memory) + 1
External
Memory
Space
No
Access
Reads
‘0’s
External
Memory
On-Chip
Memory
Space
000000h
On-Chip
Program
Memory
(Top of Memory)
(Top of Memory) + 1
External
Memory
Space
External
Memory
Mapped
to
External
Memory
Space
On-Chip
Memory
Space
000000h
On-Chip
Program
Memory
(Top of Memory)
(Top of Memory) + 1
Mapped
to
External
Memory
Space
1FFFFFh –
(Top of Memory)
1FFFFFh
1FFFFFh
1FFFFFh
Legend:
Note 1:
2:
(Top of Memory) represents upper boundary of on-chip program memory space (see Figure 5-1 for device-specific
values). Shaded areas represent unimplemented or inaccessible areas, depending on the mode.
This mode is the only available mode on 64-pin devices and the default on 80-pin devices.
These modes are only available on 80-pin devices.
TABLE 5-2: MEMORY ACCESS FOR PIC18F8XJ10/8XJ15 PROGRAM MEMORY MODES
Operating Mode
Internal Program Memory
Execution Table Read Table Write
From
From
To
External Program Memory
Execution Table Read Table Write
From
From
To
Microcontroller
Yes
Yes
Extended Microcontroller
Yes
Yes
No
No Access No Access No Access
No
Yes
Yes
Yes
DS39663A-page 58
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 2005 Microchip Technology Inc.