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UPD784938 Datasheet(PDF) 59 Page - NEC |
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UPD784938 Datasheet(HTML) 59 Page - NEC |
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59 / 733 page  CHAPTER 2 PIN FUNCTIONS 59 Preliminary User’s Manual U13987EJ1V0UM00 (a) Port mode Each port not set in the control mode can be set in the input or output mode in 1-bit units by using the port 6 mode register (PM6). (b) Control signal input/output mode (i) A16 to A19 (Address Bus) Upper address bus output pins in case of external memory space expansion (10000H to FFFFFH). These pins operate in accordance with the memory expansion 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 expansion mode register (MM). (iii) WR (Write Strobe) Pin that outputs the strobe signal for an external memory write operation. Operates in accordance with the memory expansion mode register (MM). (iv) WAIT (Wait) Wait signal input pin. Operates in accordance with the programmable wait control registers (PWC1, PWC2). (v) 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). (vi) HLDRQ (Hold Request) External bus hold request signal input pin. Operates in accordance with the hold mode register (HLDM). (vii) HLDAK (Hold Acknowledge) Bus hold acknowledge signal output pin. Operates in accordance with the hold mode register (HLDM). (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 in 1-bit units by setting the port 7 mode register (PM7). The levels of these pins can always be read or tested, regardless of the alternate-function operation. When RESET is input, port 7 is set as an input port (output high-impedance state), and the output latch contents are undefined. (9) P90 to P97 (Port 9) ... 3-state input/output Port 9 is an 8-bit input/output port with an output latch. Input/output can be specified in 1-bit units by setting the port 9 mode register (PM9). Each pin incorporates a software programmable pull-up resistor. When RESET is input, port 9 is set as an input port (output high-impedance state), and the output latch contents are undefined. |
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