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#1 10-05-2012 20:26:40

cdesp
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Location:  : Kilkis, Macedonia, Greece
Registered: 27-07-2008
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Progress

The PS/2 Keyboard scan codes are being read perfectly.
I must make a Hardware Register in order to be able to read who makes the interrupt cause now i am polling all devices
(mainly 2 rs232 and ps/2).

The Ps/2 interface uses many chips, 7 74lsxx, mainly simple gates (not,or,and) and an LS299 to buffer the Keyboard data and to put the Data line in High impedance until an input is requested from the cpu.

Also i must clear the interrupt using an 'out' after i read the keyboard scan code.

For reducing the number of chips i should use the CPLDs i have from XILINX.

 

#2 14-05-2012 20:31:02

cdesp
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Re: Progress

PS/2 keyboard interface is working ok i had to use a couple of transistors bc547 to reset the circuit after the char was read by the host cpu.
So next in line is the hardware register i have to make in order for the z80 to know who made the interrupt.
Its better to work with interrupts than with polling each device.

 

#3 27-05-2012 15:53:18

cdesp
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Re: Progress

CPLD transfer is complete. use onew of my Xilinx XC9572-10pc44 to implement the ps/2 keyboard interface.
Instead of using 6 ICs 74LSxxx and 3 Transistors i use one CPLD. It should work ok and in a smaller XC9536.

XC9500s are all obsolete and it becomes harder and harder to find so i bought 4 xc9572s from alibaba as it was the chipper source 5$ a piece + 8$ shipping costs. Last time i bought them was 3.9$/piece.
I 'll bye some xc9536s at 2,5 each ASAP.

Interrupt registers will be implemented in a cpld as mosto of logic in order to reduce Chip count and complexity.

There are a couple of pics in the gallery --> http://www.newbrain.info/component/opti … y/catid,7/

Last edited by cdesp (27-05-2012 16:14:22)

 


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