Diagnostic Board

The diagnostic board is a custom board built by Centurion technicians to make troubleshooting systems on site easier. It was designed to be compatible with CPU5 and CPU6 systems, as well as be capable of being expanded for future CPU7+ systems. However, the company went bankrupt before any further revisions could me made. As such, only one revision exists. The board documented here is serial number P02. All of the test code is stored in the four ROMs in the sockets. See the ROM Backups page or scroll to the bottom for copies of the ROM data.

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Diagnostic Tests

The Diagnostic Board features up to 16 tests, though we have only been able to confirm operation of 13 of these. The Diagnostic board features two hexadecimal LED displays to display the current test selected, error codes, or indicate a pass/fail condition. The four decimal points on the hexadecimal displays give information about the test.

• Bottom Right only: Test running

• Bottom Left and Bottom Right: Test passed

• Top Right and Bottom Right: Test failed

To initiate a test, use the DIP switch to select the test, then press the button below the DIP switch.

	Test	Notes
00	Blank
01	DMA Register Read/Write Test
02	Basic Memory Test	Writes corresponding address value to memory location
03	DMA Related Test?
04	MUX Transmit Test	Continuously write U on terminal
05	MUX Receive Test	Echoes back whatever is typed and shows parity errors on hexadecimal display
06	MUX Receive Interrupt Test	Same as Test 05 but utilizes daisy chain interrupt, card must be placed next to CPU card
07	Hawk Drive Test
08	Hawk Drive Seek Test	Seeks up through the tracks in powers of 2 before doing an RTZ and repeating
09	Hawk Drive Read Test	Seeks up through the tracks in powers of 2, reading and checking for errors
0A	TOS - Test Operating System	Click here for more details
0B	Copy of Bootstrap ROM	Only includes support for Hawk and Finch drives
0C	DIAG Board Self Test	1C if checksum fails, 2C if RAM fails, all LEDs on if passes
0D	Auxiliary Tests	See below for more details
0E	Blank?
0F	Blank?

Test 0D - Auxiliary Tests

These are higher level tests that are displayed in a Menu on the data terminal and selected/run using the keyboard. The Auxiliary Tests also use the hexadecimal displays to indicate pass/fail or show specific hex values, however they are used slightly differently than the previous tests.

• Top Left and Bottom Right: Test running

• Top Left, Bottom Left and Bottom Right: Test passed

• Top Left, Top Right and Bottom Right: Test failed

	Test	Notes
01	CUP Instruction Test
02	CPU-6 Mapping RAM Test	Test may need to be run for a very long time
03	ROM Self Test
04	CMD AUX Memory Test
05	CMD Seek Test
06	CMD Read Test
07	Floppy Command Buffer Test
08	Floppy Seek Test
09	Floppy Read Test
0A	ROM Self Test
0B	01133 CMD AUX Memory Test
0C	01133 CMD Seek Test
0D	01133 CMD Read Test
0E	Finch AUX Memory Test
0F	Finch Seek Test
10	Finch Read Test
11	ROM Self Test

Schematic

This schematic was reverse engineered by tracing out each individual line on the board itself. We are fairly confident it is mostly correct, but there could be errors still present.

Logic Design

Here is an in-depth logic diagram for the "wait state" logic. In short, the clock speed of the computer is 5MHz, which updates every 200ns. However, the PROMs on the DIAG board require 450ns before data is ready. Pins 6, 7, and 8 on the card edge connector have to do with informing the CPU whether the Data is ready or not.

Here is the Logisim file for download.

ROM Backups

The DIAG board has four ROMs that hold the code for the diagnostic tests as well as the Test Operating System (TOS). ROM F1 contains all the standard tests that show through the hex displays as well as TOS. ROMs F2, F3 and F4 contain all the Auxiliary Tests (0D) that are run through the terminal.

Board	Location	Virtual Address	Usage	IC	Link
DIAG	F1	0x8000	Diagnostic and TOS	MM2716	Link
DIAG	F2	0x8800	Auxiliary Tests	MM2716	Link
DIAG	F3	0x9000	Auxiliary Tests	MM2716	Link
DIAG	F4	0x9800	Auxiliary Tests	MM2716	Link

TOS entry point appears to be 0x8001.