Monday, January 25, 2016

Kim-IIe Requirement list

Notes for requirements for Kim-IIe card... (AIIe = Apple IIe). I am making updates to this as I think things out...
Soft switch to enable KIM card Use AIIe /DEVSEL line to enable access to a set of soft switches at AIIe $C0nx. (n =slot+$10) Either a
  • 74ls74 flip flop (1 switch)
  • 74ls259 addressable latch (8 switch)
  • 74ls75 4-bit latch (4 switch)
Enabling the card replaces AIIe $0000-$1FFF with KIM Use U7 decoder to bring AIIE /INH line low when soft switch enabled Maybe a diode on /INH connected to U7 pin 0
Make KIM Page 23 (MOS 6532) available to AIIe $Cnxx AIIe /IOSEL low enables KIM $1nxx, (without enabling /INH).
i.e: one of Kim Page 17-23 (in K4-K5) depending on the AIIe slot
Eg: card in slot 7 makes $17xx (page 23) available at AIIe $C7xx.
  1. /IOSEL activates U7 (pin 12?)
  2. XNOR A12 and U7/Q6 (otherwise, we would decode Kim $07xx)
  3. Jumper connecting U7 pin 7 (Q6) to (diode?) KIM DECEN
  4. Diode to prevent /INH from pulling low?
Decode $Cxxx-$Dxxx using a 74LS145 connected to Y6 on the main address decoder enabled by /IOSEL.
Connect outputs 0-3 to K4-K7, 4-7 to K0-K3 to make $11xx accessible at $C1xx
Make KIM K4-K5 available at $C800-$CFFF when appropriate. AIIe /IOSEL with /IOSTROBE is stored and enables KIM $1000-$17FF, mapped to $C800-$CFFF (without enabling /INH?).
  1. /IOSTROBE with /IOSEL active sets 74ls74 flip-flop.
  2. Jumper connecting U7 pin 7 (Q6) to KIM DECEN.
  3. output of flip-flop activates 74LS145 added above.
  4. Another address decoder or 74LS133 resets flip-flop when CFFF is on the Address bus.
  5. UGH, too much stuff...
KIM access to soft switches Hmmm... Hmmm...
XNORing A12 to invert its signal when /DEVSEL is active took too many chips and got too confusing.
Since /IOSEL is only active in the $Cn00 range, we don't need to connect the new 74LS145 to the main address decoder.

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