CHAPTER 2 PIN FUNCTIONS
(a) Port mode
PCT0, PCT1, PCT4, and PCT6 can be set to input or output in 1-bit units by the port CT mode register
(PMCT).
(b) Control mode
PCT0, PCT1, PCT4, and PCT6 can be set to the port mode or control mode in 1-bit units by the PMCCT
register.
(i) WR0 (lower byte write strobe) ... Output
This is the write strobe signal output pin for the lower data of the external 16-bit data bus.
(ii) WR1 (upper byte write strobe) ... Output
This is the write strobe signal output pin for the higher data of the external 16-bit data bus.
(iii) RD (read strobe) ... Output
This is the strobe signal that indicates that the bus cycle currently being executed is a read cycle for
the external memory or external peripheral I/O. In the idle state (TI), this pin is inactive.
(iv) ASTB (address strobe) ... Output
This is the latch strobe signal output pin for the external address bus.
The output becomes low level in synchronization with the falling edge of the clock in the T1 state of
the bus cycle, and becomes high level in synchronization with the falling edge of the clock in the T3
state.
(11) PDH0 to PDH5 (Port DH) ... I/O
Port DH is a 6-bit I/O port that can be set to input or output in 1-bit units.
In addition to functioning as a port, PDH0 to PDH5 can also be used as an address bus (A16 to A21) when the
memory is expanded externally in the control mode (external expansion mode).
The port mode and control mode can be selected as the operation mode for each bitNote, and are specified by
the port DH mode control register (PMCDH).
Note When specifying the port mode/control mode (alternate function) for each bit, pay careful attention to
the operation of the alternate functions.
(a) Port mode
PDH0 to PDH5 can be set to input or output in 1-bit units by the port DH mode register (PMDH).
(b) Control mode
PDH0 to PDH5 can be used as A16 to A21 by the PMCDH register.
(i) A16 to A21 (address bus) ... Output
These are the higher 6-bit address output pins within a 22-bit address on the address bus during
external access.
(12) PDL0 to PDL15 (Port DL) ... I/O
Port DL is a 16-bit I/O port that can be set to input or output in 1-bit units.
User’s Manual U15862EJ3V0UD
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NEC [ NEC ]
