The first IDE interface for the Coupé.
Originally designed by Ian Spencer from an article in the Spectrum und Sam Profi Club magazine by Roelof Koning.
Originally designed to run Search: “HDUTIL” to have a carosel of virtual disk images that could be loaded into a One Meg expansion as a virtual drive it was extended into Search: “HDUI” with support for loading, saving and directory navigation.
The design was offered to and productionised with a PCB by Nev Young.
This first release had bugs due to the missing out of an LS245 buffer chip causing unreliable operation, excess load on the SAM data lines and inconsisencies with timing. This needed to be fixed with a recall and hardware modification.
Nev developed HDOS as a more native IDE solution although lack of integration with BASIC and the recall issued was a hurdle to user adoption along with the release of the ATOM.
R1 - 100R 0.25W
R2-5 - 4K7 0.25W
R6-8 - 10K
C1-C3 - 100nF Ceramic
C4 - 1nF Ceramic
D1 - 3mm LED Red
IC1, IC5 - 74HC245 Tri-State Octal Bus 8-bit transceiver
IC2, IC4 - 74HCT574 Tri-State Octal D-type flip-flop
IC3 - 74LS374 Tri-State Octal D-type flip-flop Edge
IC6, IC10 - 74LS32 Quadruple 2-Input Positive-OR Gate
IC7, IC9 - 74LS688 8-bit identirty comparitor
IC8 - 74LS74 Dual D-type flip-flop with preset and clear
CONN1 - 64 Way 2.54mm Pitch, Type C Class C3, 2 Row, Right Angle DIN 41612 Connector, Plug
CONN2 - Right angled 40 way IDC male socket for IDE
Resistors 10K x 3
Bug Fix Version
The IDE interface was unbuffered meaning that long IDE cables could cause issues with data loss and corruption.
A version of SC_WORD pro supported the interface.