8-bit ISA debug and POST card

 

ISA debug post card with additional features like data/address bus analyzer, frequency measure and multi I/O POST port selection. Uses a XC95144XL CPLD as main IC.

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Special thanks to PCBWay!

Special thanks to PCBWay for sponsoring this project! PCBWay is a well-known PCB prototyping and manufacturing service, providing high-quality boards and excellent customer support. I have worked with their boards in the past and can say that they are of great quality. The sponsorship also included a free quick delivery option. If you’re looking for reliable PCB prototyping and manufacturing services, I highly recommend checking them.

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History

Same story as with the 8-bit ISA protoboard; I didn't have an ISA POST card. After building a prototype on a protoboard, I received sponsorship from PCBWay for proper PCBs, which allowed me to turn this card into a "full product"!

Links

Schematic and PCB design files: https://github.com/maniekx86/isa_debug_post_card
VHDL sources: https://github.com/maniekx86/isa_debug_post_card_cpld_source

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Usage and features

SW1 (Card mode)

1	2	3	Mode	Description
-	-		POST analyzer	Default POST analyzer mode, captures last 3 POST codes
ON	-	-	Data bus analyzer (D0-D7)	Data bus analyzer, displays current value on data bus D0-D7
ON	-	ON	Address bus analyzer (A0-A19)	Address bus analyzer, displays current value on address bus (A0-A19)
-	ON	-	ISA CLK frequency counter (ISA CLK)	Frequency counter, displays frequency of ISA CLK signal
-	ON	ON	ISA OSC frequency counter (14.318 MHz OSC)	Frequency counter, displays frequency of OSC signal (14.318MHz)
ON	ON		Display current set POST port (SW2)	Displays current captured POST port set by SW2

- = OFF, empty = don't care

SW2 (Captured POST I/O port)

1	2	3	POST Port	Notes (used by)
-	-	-	80h	Standard, AT‑class (IBM AT, clones)
ON	-	-	84h	Compaq models
-	ON	-	90h	PS/2 Model 25 & 30
ON	ON	-	300h	Some Award BIOSes and clones
-	-	ON	680h	MCA‑bus PS/2 systems
ON	-	ON	60h	XT machines
-	ON	ON	190h	Some PS/2 or EISA variants
ON	ON	ON	378h	LPT1 (e.g., Olivetti diagnostics)

 

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Assembly instructions

Refer to the image below

Bill of materials:

Marking(s)	Element	Amount
U3	XC95144XL	1
U4	ULN2803	1
U5	74244	1
U2	LM1117T-3.3V	1
Y1	20 MHz crystal oscillator, DIP-8 or DIP-14	1
SW1, SW2	DIP switch x3	2
Q1, Q2, Q3, Q4, Q5, Q6	BC556 or BC557	6
U6, U7	3-digit 0.56 inch 7-segment display with common anode (can be found as 5631BS)	2
D1, D2, D3, D4, D5, D7, D8, D10, D11	Red LED, 5mm	9
D6, D9	Yellow LED, 5mm	2
C2, C3, C5, C6, C7, C8, C9, C10	0.1 µF capacitor	8
C1, C4	22 µF capacitor (doesn't need to be 22 µF, can be in range from 10 to 47 µF)	2
R1, R2, R3, R4, R7, R8, R9, R10	100 Ω resistor	8
R5, R6, R11, R12, R22, R23, R17, R13, R15, R14, R18, R19	1 KΩ resistor	12
R28, R20, R24, R30, R25, R31, R16, R21, R27	1.2 KΩ resistor. The used value can differ based on the desired brightness of the red LEDs	9
R29, R26	2.2 KΩ resistor. The used value can differ based on the desired brightness of the yellow LEDs	2
J2	6-pin male gold pin connector (JTAG)	1
J3	1-pin male gold pin connector (GND)	1

 

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