keyboard

Hi all,

Now its time to talk about the keyboard, I did a little search in all my city's shop waste to find an used piece, and after a long time I found one, it belongued to a POS(Point Of Sale) it is from Itautec model PDV 54 keys and i payed only $5 bucks.
It will be enough for my project as I am thinking to make monitor's program to help in programming the z80.


At the right side you can see the part that will be used to input program z80's memories.
The keys 0 .. F (hexadecimal ) input







The keyboard's schematic.

I did some modifications to the printed board to facilitate the key reading, and in the end it is like the schematic above.

The z80 system clock

My z80 system will be started in a section named OpenZ80, the clock, that I had so many doubts about it, as I used to work with moderns microcontrollers and clock does not need to be so clear, and I read that z80 needs a clean clock and reset, I decided to use an attiny15L that I have some pieces here. This chip will provide several clocks for the system and configuring 2 pins it is possible to change betwen them. The clock values are: 12Mhz, 6Mhz, 3Mhz and 1,6Mhz no need to say that all of them will not have the precise value, because the attiny15l has a pll that generate 25Mhz that is divided to get these values Another feature is: 1 - the reset pulse to the z80, this reset will maintain the z80 for a long time in logic level zero when the power supply is turned on. 2 - led blinking, this is just to sinalize that the system is on, Image 01 - Clock Attiny15L - Assembler code to generate: clock, reset and blink led

 
; Program....: reset.asm
; Description: Z80 reset, clock 1,6Mhz, 3,2Mhz, 6,4Mhz or 12,8Mhz
; Author.....: Paulo da Silva
; Date.......: 26/09/2016
; 
; Attiny15L
;        +----+
;   rst--|    |-- vcc;
; cfg1 --|    |-- led blink
; cfg2 --|    |-- z80 clock
;   gnd--|    |-- z80 reset
;        +----+
;                                           
;    cfg2 cfg1                                      
;     0    0  ->   12,8Mhz                           
;     0    1  ->    6,4Mhz                  
;     1    0  ->    3,2Mhz                      
;     1    1  ->    1,6Mhz   
;
; Assembler: avra version 1.3.0 build 1
; Command..: avra reset.asm
.nolist
.include "/usr/share/avra/tn15def.inc"
.list
;==============
; Declarations
; PB0 - reset for z80
; PB1 - z80`s clock
; PB2 - led blink
; PB3 - Clock`s Configuration bit 1 (cfg1)
; PB4 - Clock`s Configuration bit 2 (cfg2)
;=================
; Variable Declarations
.equ OSCCAL_val = 0x6F  ; Calibrate
.def cseg       = r21  
.cseg      ; Code segment.
; Start of Program
.org    0
 rjmp Init   ; First line executed
 reti     ; IRQ0 handler
 reti     ; Pin change handler
 rjmp timer1CM  ; Timer1 compare match
 reti     ; Timer1 overflow handler
 rjmp timer0;  ; Timer0 overflow handler    
 reti     ; Eeprom Ready handler
 reti     ; Analog Comparator handler
 reti     ; ADC Conversion Handler
;============
Init:
 ; writing calibration byte to the OSCCAL Register.
 ldi     r16, OSCCAL_val
 out     OSCCAL, r16       
 nop
 nop
 ;Analogue comparator initialization
 ldi      r16, 0b10000000  ; Disable analogue comparator
 out      ACSR, r16
 ;PORTB initialization
 ldi      r16, 0b00000111  ; 1 = output e 0 =input1/6
 out      DDRB, r16    ; pb0 and pb1 = output pb2 = input
 ldi      r16, 0b11111000
 out      PortB, r16
 ;Timer initialization
 ldi      r16, 0x05   ; Timer 0 rolls over at 1.6MHz/1024/256 = 6.1Hz
 out      TCCR0, r16
 
 ;timer 1
 in    r16, PinB   ; Input port b to read clock configuration
 andi  r16, 0b00011000          ; pb3 and pb4
 cpi   r16, 0b00000000  ; 00 = 12,847Mhz
 brne  test6mhz
 ldi   r16, 0b10010001  ; 12Mhz
 rjmp  init2 
test6mhz: 
 cpi   r16, 0b00001000  ; 01 = 6Mhz
 brne  test3mhz
 ldi   r16, 0b10010010  ; 6,396 Mhz
 rjmp  init2  
test3mhz: 
 cpi   r16, 0b00010000  ; 10 = 3Mhz
 brne  test1mhz
 ldi   r16, 0b10010011  ; 3,210Mhz
 rjmp   init2
test1mhz: 
 ldi   r16, 0b10010100  ; 1,605Mhz
init2:
 out   TCCR1, r16
 ldi   r16, 0b00000000
 out   TCNT1, r16
 
 ldi      r16, $02  ;  Enable TOVF0
 out      TIMSK, r16  
 ldi      cseg, $01  ; Start at segment
 ldi      r17, 0x00
 ldi      r16, 0x00
 sei                  ; Enable Interrupts          
;======================
; Main body of program:
Main:            
loopRst:
 cbi  PortB, pb0 
 cpi  r16, 6  ; Wait some time here before to raise z80's reset line 
 brne loopRst
 sbi  PortB, pb0
blink:
 ;blink a led
 SBRS    r16, 0  ;2 Skip next instruction if bit0 = 1
 SBI     PORTB, pb2 ;2 Turn LED ON if bit0 = 0
 SBRC    r16, 0  ;2 Skip next instruction if bit0 = 0
 CBI     PORTB, pb2 ;2 Turn LED OFF if bit0 = 1
 rjmp    blink   ;2 loops back to the start of Main
 
timer0:
 inc  r16   ;Increment and will be used to blink a led
 reti
    
timer1CM:

This is tested !!! :) Enjoy

The complete system list at least for while

They are a sketch by this they can change any time.

1 - The z80 clock
2 - Addressing system
3 - Static memory(SRAM) 32kbytes minimal
4 - Eprom memory(8kbytes)
5 - I/O system(bip sound, rs232, spi interface)
6 - SDcard (at least 8gb)
7 - keyboard and 6 display 7 segments and LCD maybe 4lines 20 characters
8 - CPU Z80 8Mhz and I/O expansion bus

Greetings !!

Hi all,

Wecome to my blog!

It is the first time that I will share my things, so I hope you enjoy all of them.

Here I'll try to publish all my projects of hardware and software, specially the embedded one.
My first project is a z80 system made by me, I know that outside there has a lot of this kind of project but mine is a long time desire,since I was attending an electronic technician course so don't blame me to realize it.

:) Enjoy !!!