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CHAPTER 2 PIN FUNCTIONS
(a) Port mode
Each port pin not set in the control mode can be set in the input or output mode by using the port 9 mode register
(PM9).
(b) Control signal I/O mode
(i) RD (Read Strobe)
This pin outputs a strobe signal to read an external memory. The operation of this pin is specified by the
memory extension mode register (MM).
(ii) LWR, HWR (Low/High Write Strobe)
These pins output strobe signals to write an external memory. The operations of these pins are specified
by the memory extension mode register (MM).
(iii) ASTB (Address Strobe)
This is a timing signal output pin to latch the address information output from the AD0 through AD15 pins
to access the external memory. The operation of this pin is specified by the memory extension mode
register (MM).
(iv) WAIT (Wait)
This pin inputs a wait signal. The operation of this pin is specified by the port 9 mode control register
(PMC9).
(11) BWD (Bus Width Definition) ... Input
This pin specifies the width of the bus. Depending on the setting of this pin, the value of the bus width specification
register (BW) at reset differs as follows:
BWD
External Bus Width
Value of BW at Reset
0
8 bits
0000H
1
16 bits
00FFH
(12) MODE (Mode) ... Input
This pin is used by NEC for testing IC. Be sure to directly connect this pin to V
SS
.
(13) CLKOUT (Clock Output) ... Output
Clock output. Low level is output in the IDLE mode or STOP mode, otherwise f
XX
(oscillation frequency) is always
output
(14) X1, X2 (Crystal)
These pins are used to connect a crystal for internal clock oscillation. To supply an external clock, input the clock
to the X1 pin. For the processing of the X2 pin at this time, refer to
CHAPTER 4 CLOCK GENERATOR
.
(15) RESET (Reset) ... Input
Active-low reset input
(16) AV
REF
(Analog Reference Voltage)
This pin inputs a reference voltage to the A/D converter.