
CHAPTER 3 CPU FUNCTION
82
User’s Manual U14359EJ4V0UM
3.4.6
External memory expansion
By setting the port n mode control register (PMCn) to control mode, an external memory device can be connected
to the external memory space using each pin of ports AL, AH, DL, CS, CT, CM, and CD. Each register is set by
selecting control mode for each pin of these ports using PMCn (n = AL, AH, DL, CS, CT, CM, CD).
Note that the status after reset differs as shown below in accordance with the operating mode specification set by
pins MODE0 to MODE2 (refer to
3.3 Operating Modes
for details of the operating modes).
(a) In the case of ROMless mode 0
Because each pin of ports AL, AH, DL, CS, CT, CM, and CD 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 ROMless mode 1
Because each pin of ports AL, AH, DL, CS, CT, CM, and CD 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 8 bits).
(c) In the case of single-chip mode 0
After reset, since the internal ROM area is accessed, each pin of ports AL, AH, DL, CS, CT, CM, and CD
enters the port mode and external devices cannot be used.
To use external memory, set the port n mode control register (PMCn).
(d) In the case of single-chip mode 1
The internal ROM area is allocated from address 100000H. As a result, because each pin of ports AL,
AH, DL, CS, CT, CM, and CD 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).
Remark
n = AL, AH, DL, CS, CT, CM, CD
Содержание V850E/MA1
Страница 2: ...2 User s Manual U14359EJ4V0UM MEMO...