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ULA (Named HCS 10017)

There is no official datasheet (impossible to find one on the internet).

This chip needs a 12 MHz clock on its CLK_IN pin. CLK_OUT pin sents an 1 MHz clock to the CPU.

  • D0-D7 Data bus (only read no write from ULA)
  • Red, Blue, Green : RGB signals
  • VSS : 5V
  • A8 to A15 Address bus
  • MA0 to MA7 : address bus RAM
  • W write signal for RAM
  • Mux : external multiplexer command
  • Sync : Sync video signal
  • MAP : Disable/enable internal decoding address bus ?
  • CLK_IN : 12 MHz
  • CLK_OUT : 1 MHz

* Mux is high when CLKOUT is high : This means that the address from the cpu are ok. This means that mux will help to switch A0 to A7 and MA0 to MA7. If MUX=1 : A0 to A7 are enabled with RAS. If Mux=0 MA0 and MA7 are enabled by cas.

* MA0 and MA7 outputs are a mirror of A8 to A15 inputs. Ula generate RAS, CAS and W : It needs to inverts MA0, MA7 to run normally

* when Mux is low, it's the graphics part of the ULA which access to ram to draw the screen

* in the case of an access from #0300 to #03FF, or #C000 TO #FFFF, the chip does not generate CAS signal. (fig4)

* MAP signal must be forced to 1, in normal configuration. If MAP switched to 0, it allow to access to shadow ram (#C000 TO #FFFF)

Fig 4

Fig 3

oric/hardware/ula_10017.txt · Last modified: 2011/03/06 04:47 by polluks