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27. Precautions (Bus)
27.3 Bus
__________
27.3.1 HOLD Signal
When entering microprocessor mode or memory expansion mode from single-chip mode and using
__________
HOLD input, set the PM01 and PM00 bits to "112" (microprocessor mode) or to "012" (memory expansion
mode) after setting the PD4_7 to PD4_0 bits in the PD4 register and the PD5_2 to PD5_0 bits in the PD5
register to "0" (input mode).
_____
_______
______ ______ ________ ______ _______
________
P40 to P47 (A16 to A22, A23, CS0 to CS3, MA8 to MA12) and P50 to P52 (RD/WR/BHE, RD/WRL/WRH)
__________
are not placed in high-impedance states even when a low-level ("L") signal is applied to the HOLD pin, if
the PM01 and PM00 bits are set to "112" (microprocessor mode) or to "012" (memory expansion mode)
after setting the PD4_7 to PD4_0 bits in the PD4 register and the PD5_2 to PD5_0 bits in the PD5 register
to "1" (output mode) in single-chip mode.
27.3.2 External Bus
The internal ROM cannot be read when a high-level ("H") signal is applied to the CNVSS pin and the
hardware reset (hardware reset 1 or brown-out detection reset) occurs.