CHAPTER 2 PIN FUNCTIONS
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(b) Control signal input/output mode
(i)
A16 to A19 (Address Bus)
Upper address bus output pins in case of external memory space extension (10000H to FFFFFH).
These pins operate in accordance with the memory extension mode register (MM).
(ii)
RD (Read Strobe)
Pin that outputs the strobe signal for an external memory read operation.
Operates in accordance with the memory extension mode register (MM).
With the
μ
PD784031, this pin always serves as an RD pin.
(iii) WR (Write Strobe)
Pin that outputs the strobe signal for an external memory write operation.
Operates in accordance with the memory extension mode register (MM).
With the
μ
PD784031, this pin always serves as a WR pin.
(iv) WAIT (Wait)
Wait signal input pin. Operates in accordance with the programmable wait control registers (PWC1, PWC2).
(v)
HLDRQ (Hold Request)
External bus hold request signal input pin. Operates in accordance with the hold mode register
(HLDM).
(vi) HLDAK (Hold Acknowledge)
Bus hold acknowledge signal output pin. Operates in accordance with the hold mode register
(HLDM).
(vii) REFRQ (Refresh Request)
This pin outputs refresh pulses to pseudo-static memory when this memory is connected
externally. Operates in accordance with the refresh mode register (RFM).
(8) P70 to P77 (Port 7) ... 3-state input/output
Port 7 is an 8-bit input/output port. In addition to operating as an input/output port, it also operates as the A/D converter
analog input pins (ANI0 to ANI7).
Input/output can be specified bit-wise by means of the port 7 mode register (PM7).
The levels of these pins can always be read or tested, regardless of the operation of the multiplexed pins.
When RESET is input, port 7 is set as an input port (output high-impedance state), and the output latch contents are
undefined.
(9) ASTB (Address Strobe)/CLKOUT (Clock Output) ... Output
This pin outputs the timing signal that latches address information externally in order to access an external address. It also
operates as the pin that supplies the clock to an external device.
With the
μ
PD784031, CLKOUT cannot be used.
(10) X1, X2 (Crystal)
The internal clock oscillation crystal connection pins. When the clock is supplied externally, it is input to the X1 pin. Usually
signal with the inverse phase of the X1 pin signal phase is input to the X2 pin (Refer to
4.3.1 Clock oscillation circuit
).