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3886 Group User’s Manual
HARDWARE
PROCESSOR MODE
Single-chip mode, memory expansion mode, and microprocessor
mode in the M38867M8A/E8A can be selected by changing the
contents of the processor mode bits (CM0 and CM1 : b1 and b0 of
address 003B16). In memory expansion mode and microprocessor
mode, memory can be expanded externally through ports P0 to
P3. In these modes, ports P0 to P3 lose their I/O port functions
and become bus pins.
Fig. 64 Memory maps in various processor modes
Fig. 65 Structure of CPU mode register
(1) Single-chip mode
Select this mode by resetting the microcomputer with CNVSS con-
nected to VSS.
(2) Memory expansion mode
Select this mode by setting the processor mode bits (b1, b0) to
“01” in software with CNVSS connected to VSS. This mode enables
external memory expansion while maintaining the validity of the in-
ternal ROM.
However, do not set this mode in the M38869M8A/MCA/MFA and
the flash memory version.
(3) Microprocessor mode
Select this mode by resetting the microcomputer with CNVSS con-
nected to VCC, or by setting the processor mode bits to “10” in
software with CNVSS connected to VSS. In microprocessor mode,
the internal ROM is no longer valid and external memory must be
used.
Do not set this mode in the M38869M8A/MCA/MFA and the flash
memory version.
Port Name
Port P0
Port P1
Port P2
Port P3
Function
Outputs low-order 8 bits of address.
Outputs high-order 8 bits of address.
Operates as I/O pins for data D7 to D0
(including instruction code).
P30 and P31 function only as output pins
(except that the port latch cannot be read).
P32 is the ONW input pin.
P33 is the RESETOUT output pin. (Note)
P34 is the
φ output pin.
P35 is the SYNC output pin.
P36 is the WR output pin, and P37 is the RD out-
put pin.
Table 17 Port functions in memory expansion mode and
microprocessor mode
Note : If CNVSS is connected to VSS, the microcomputer goes to single-
chip mode after a reset, so that this pin cannot be used as the
RESETOUT output pin.
FUNCTIONAL DESCRIPTION
XXXX16
000016
004016
000816
000016
YYYY16
FFFF16
000816
004016
FFFF16
Internal RAM
reserved area
Internal ROM
Memory expansion mode
The shaded area are external memory area.
SFR area
XXXX16 indicates the last address of internal RAM.
YYYY16 indicates the first address of internal ROM.
SFR area
Microprocessor mode
*
*:
Internal RAM
reserved area
XXXX16
**
b0
CPU mode register
(CPUM : address 003B16)
Processor mode bits (CM1, CM0)
b1 b0
0
0: Single-chip mode
0
1: Memory expansion mode (Note)
1
0: Microprocessor mode (Note)
1
1: Not available
Stack page selection bit
0: 0 page
1: 1 page
b7
Note: This is not available for the products except
M38867M8A/E8A.