CHAPTER 2 PIN FUNCTIONS
User’s Manual U12688EJ4V0UM00
61
(14) PA0 to PA7 (Port A) ··· 3-state I/O
Port A is an 8-bit input/output port that can be set to input or output in 1-bit units.
Besides functioning as a port, in the control mode (external expansion mode) it operates as an address bus
(A0 to A7) when memory is externally expanded.
The operation mode is specified by the mode specification pins (MODE0 to MODE3) and the memory
expansion mode register (MM).
(a) Port mode
PA0 to PA7 can be set to input or output in bit units by the port A mode register (PMA).
(b) Control mode (External expansion mode)
PA0 to PA7 can be set as A0 to A7 by using the MODE0 to MODE3 pins and MM register.
(i)
A0 to A7 (Address) ··· output
These pins constitute the address bus that is used for external access. The output changes in
synchronization with the falling of the CLKOUT signal in the T1 state of the bus cycle. In the idle
state (TI), the previous bus cycle’s address is held.
(15) PB0 to PB7 (Port B) ··· 3-state I/O
Port B is an 8-bit input/output port that can be set to input or output in 1-bit units.
Besides functioning as a port, in the control mode (external expansion mode) it operates as an address bus
(A8 to A15) when memory is externally expanded.
The operation mode can be set as port or control in 2-bit or 4-bit units, specified by the mode specification pins
(MODE0 to MODE3) and memory expansion mode register (MM).
(a) Port mode
PB0 to PB7 can be set to input or output in bit units by the port B mode register (PMB).
(b) Control mode (External expansion mode)
PB0 to PB7 can be set as A8 to A15 by using the MODE0 to MODE3 pins and MM register.
(i)
A8 to A15 (Address) ··· output
These pins constitute the address bus when the external memory is accessed.
The output changes in synchronization with the rising edge of the CLKOUT signal in the T1 state of
the bus cycle. In the idle state (TI), the impedance becomes high.
Содержание V850E/MS1 UPD703100
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