Update Sept 2022 - John's Vademecum

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====== Update Sept 2022 ======

** Some recent modifications and additions **

===== Hardware =====

  * 2 more 65C22 VIA chips to give a total of 3 VIAs providing six 8-bit I/O ports.
    * VIA #1 ($6001) : Port A = Keypad
    * VIA #1 ($6000) : Port B = LCD_1 (4x20 in 4-bit mode)
      * VIA #1 : IRQ connection to CPU for keypad and CB1 & CB2 buttons
      * VIA #1 Port B handshaking CB1 and CB2 connected to debounced buttons for user input experiments
    * VIA #2 ($5001) : Port A = Spare
    * VIA #2 ($5000) : Port B = SPI (bit0,1,2,6), Piezo Sounder (bit7)
      * VIA #2 : T1 Timer = square wave generator for sounder using Port B bit7
    * VIA #3 ($4801) : Port A = LCD_2 (2x16 in 4-bit mode)
    * VIA #3 ($4800) : Port B = Spare
      * VIA #3 : T1 Timer = System Clock Ticks at 10ms rate via NMI connection to CPU
  * main LCD changed to a 4 line by 20 character display
  * 2nd LCD (2 x 16) added on VIA #3 Port A
  * LED indicator plug-in boards made to give easy visual indication of VIA output port state
  * Piezo sounder connected to VIA #2 Port B, bit 7
  * SPI interfacing using VIA #2 Port B
  * Buttons for controlling interrupt driven events, each de-bounced with a 555 monostable
  * 555 timer as a power-on CPU reset

===== Firmware =====

ROM Monitor code extended to support the new hardware.

  * SPI transceive to communicate with a basic SPI slave running on a PyBoard
  * LCD #2 display of either "Mission Time" or SPI TX/RX data to/from PyBoard
  * code to send audible beeps of different pitch/duration (controlled by the 2 buttons)
  * keypad - confirmation keypress beeps
  * Byte (binary) to ASCII decimal conversion to show 16-bit/2-byte binary data as a human readable decimal number
  * Use of FLAGS to control background tasks extended/explored

===== Next Steps =====

  * add Serial Interface using Rockwell 65C51 ACIA and MAX232
  * learn how to code for interacting via serial interface
  * connect to a Wyse-185 Serial Terminal
  *<todo #john:2022-09-26>add DS1306 RTC via SPI</todo>
  *<todo #john:2022-09-26>move system clock back to VIA_1 using IRQ interrupt</todo>
  *<todo #john:2022-09-26>move beep to VIA_3 port B7</todo>
  * <todo #john:2022-09-26>move SPI interface to VIA_3 port B, for future connection to DS1306 RTC</todo>
    * this will leave :
      * VIA_2 ports A & B free for external use
      * VIA_3 Port A = LCD2
      * VIA_3 Port B = Beep and SPI/RTC


--- //John Pumford-Green 17/09/22 11:50//


===== Further Information =====


{{tag>6502 assembly}}
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