CHAPTER 3 CPU FUNCTION
65
User’s Manual U15195EJ5V0UD
3.4.6
External memory expansion
By setting the port n mode control register (PMCn) to control mode, an external device can be connected to the
external memory space using each pin of ports DH, DL, CT, and CM. Each register is set by selecting control mode
for each pin of these ports using PMCn (n = DH, DL, CT, CM).
Note that the status after reset differs as shown below in accordance with the operating mode specification set by
the MODE0 and MODE1 pins (refer to
3.3 Operation Modes
for details of the operation modes).
(a) In the case of ROMless mode
Because each pin of ports DH, DL, CT, and CM enters control mode following a reset, external memory
can be used without making changes to the port n mode control register (PMCn) (the external data bus
width is 16 bits).
(b) In the case of single-chip mode
Since the internal ROM area is accessed after a reset, each pin of ports DH, DL, CT, and CM enters the
port mode, and external devices cannot be used.
To use external memory, set the port n mode control register (PMCn).
Remark
n = DH, DL, CT, CM
Содержание PD703114
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