Setting Processor Modes - Renesas 7700 FAMILY User Manual

CENTRAL PROCESSING UNIT (CPU)
2.5 Processor modes

2.5.3 Setting processor modes

The voltage supplied to the CNVss pin and the processor mode bits (bits 1 and 0 at address 5E
processor mode.
When Vss level is supplied to CNVss pin
After a reset, the microcomputer starts operating in the single-chip mode. The processor mode is switched
by the processor mode bits after the microcomputer starts operating. When the processor mode bits are
set to "01 ," the microcomputer enters the memory expansion mode; when these bits are set to "10
2
the microcomputer enters the microprocessor mode.
The processor mode is switched at the rising edge of signal E after writing to the processor mode bits.
Figure 2.5.3 shows the timing when pin functions are switched by switching the processor mode from the
single-chip mode to the memory expansion or microprocessor mode with the processor mode bits.
When the processor mode is switched during the program execution, the contents of the instruction
queue buffer is not initialized. (Refer to "Appendix 9. Q & A.")
When Vcc level is supplied to CNVss pin
After a reset, the microcomputer starts operating in the microprocessor mode. In this case, the microcomputer
cannot operate in the other modes. (Fix the processor mode bits to "10
Table 2.5.2 lists the methods for setting processor modes. Figure 2.5.4 shows the structure of processor
mode register 0 (address 5E
Note: Functions of pins P0
Function of pin P4
microprocessor mode.
Fig. 2.5.3 Timing when pin functions are switched
2–26
).
16
Written to processor mode bits
E
Programmable I/O port P0
P0
0
to P0 , P1 to P3, P4
1 7
is, however, switched only when the processor mode is switched to the
2
7751 Group User's Manual
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External address bus A
0
to P4 are switched at the same timing shown above.
0 2
16
.")
2
0
) set the
,"
2