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3.4.6 External expansion mode
The V850/SA1 allows external devices to be connected to the external memory space by using the pins of ports 4,
5, 6, and 9. To connect an external device, the port pins must be set in the external expansion mode by using the
memory expansion mode register (MM).
The address bus (A1 to A15) is set to maltiplexed output with data bus (D1 to D15), though separate output is also
available by setting the memory address output mode register (MAM) (See the User's Manual of relevant in-circuit
emulator about debagging when using the separate bus).
Because the V850/SA1 is fixed to single-chip mode in the normal operation mode, the port/control mode alternate
pins become the port mode, thereby the external memory cannot be used. When the external memory is used
(external expansion mode), specify the MM register by the program.
(1) Memory expansion mode register (MM)
This register sets the mode of each pin of ports 4, 5, 6, and 9. In the external expansion mode, an external
device can be connected to the external memory area of up to 4 Mbytes. However, the external device cannot be
connected to the internal RAM area, on-chip peripheral I/O area, and internal ROM area in the single-chip mode
(access is restricted to external locations 100000H through FFE00H).
The MM register can be read/written in 8- or 1-bit units. However, bits 4 to 7 are fixed to 0.
CHAPTER 3 CPU FUNCTIONS
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