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CHAPTER 3 CPU FUNCTIONS
User’s Manual U15109EJ3V0UD
103
3.4.6 External expansion mode
The V850/SC1, V850/SC2, and V850/SC3 allow external devices to be connected to the external memory space
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 using the memory expansion mode register (MM).
In the V850/SC1 and V850/SC2, the address bus (A1 to A15) is set to multiplexed output with the data bus (D1 to
D15), however, separate output is also available by setting the memory address output mode register (MAM) (see the
User’s Manual of the relevant in-circuit emulator about debugging when using the separate bus).
Caution
Because the A1 pin and WAIT pin are alternate-function pins for the V850/SC1 and V850/SC2, the
WAIT pin based wait function cannot be used when using a separate bus (programmable wait
can be used, however). Similarly, a separate bus cannot be used when the WAIT pin based wait
function is being used.
Because the V850/SC1, V850/SC2, and V850/SC3 are fixed to single-chip mode in the normal operating mode, the
pins related to the bus interface are set to port mode, disabling use of the external memory. When the external
memory is used (external expansion mode), specify the MM register or MAM register by program (for the V850/SC1
and V850/SC2) or specify the MM register by program (for the V850/SC3).