This is a DEC AX08 Laboratory Peripheral manufactured on October 28th 1970, serial number 327. It has the following functions 9 bit multiplexed input analog to digital (A/D) converter with up to 24 input channels, crystal and R/C clocks, up to 3 adjustable Schmitt trigger pulse input, up to 8 digital pulse inputs, and up to 4 digital outputs. It also had a point plot display output. Digital first started selling these units in 1967.
The point plot output was used to drive an oscilloscope. Later X/Y deflection monitors like VR14 were used. The display is generated by the processor specifying an 9 bit X and Y location and then requesting that a spot be drawn on the CRT at that location. It then repeates this process to draw the entire display with out of a bunch of dots. On the VR14 link above are pictures and videos of the display from the similar VC8E point plot display for the PDP-8/E. The entire display would need to be redrawn at a 30-60Hz rate to prevent flicker.
The successive approximation (more) type of A/D converter uses a digital to analog (D/A) converter as part of its operation. To save cost the same D/A converter is used for the analog to digital converter and the point plot display. The AX08 gives precedence to the A/D conversion so the point plot display can't be refreshed while an A/D conversion was in process.
The timing of the AX08 is either controlled by a crystal clock with a period of 100 microseconds or a RC clock with an adjustable period of 20 microseconds to 2 Seconds in 11 ranges. These clocks can be used for software timing and be used as the A/D converter sample clock.
The Schmitt trigger digital pulse inputs have an adjustable threshold of -.5 to -2.5 volts and a .7 volt hysteresis. A bit in a register is set when they cross the lower threshold generate an interrupt to the processor if enabled. The 8 "contingency" inputs set bits in the external register when they are at ground.
| General | |
|---|---|
| Size (HeightxWidthxDepth) | 10.5x19x18.75 |
| Weight | TBD |
| Power | Type 728 or 779 Power supply 10V TBD A, -15V TBD A |
| Operating Temperature | 0 to 50C | A/D Converter Specifications |
| Word Length | 9 bits |
| Type | Successive approximation |
| Accuracy | +- 1/2 LSB +- .2% |
| Speed | <= 17 microseconds |
| Sample & Hold Speed | full scale track in 2 microseconds |
| Input | +-1.024V full scale 50K input impedance |
| Speed | <= 17 microseconds |
| Format | 2's complement |
| Input Channels | 4 standard 24 maximum |
Point Plot Specifications |
| Resolution | 9 bits |
| Intensity Control | 1 bit standard 3 bits optional |
| X & Y Output | 0 to -10V |
| Intensity Output | TBD |
The following picture links below also have descriptions of what is show in the pictures.
Front view ( 39K)
Rear of front panel ( 59K)
Top view ( 93K)
Left side ( 53K)
Right side ( 57K)
Bottom view (118K)
Backplane closeup (140K)
Back view ( 34K)
Labels ( 21K)
| Quantity | Board Type | Description |
|---|---|---|
| 2 | A130 | |
| 1 | A202 | |
| 1 | A401 Sample and Hold | |
| 1 | A502 | |
| 2 | A601 3 Bit DAC | |
| 6 | A604 | |
| 1 | A704 Reference Supply | |
| 1 | A706 Power Supply | |
| 1 | R002 Diode Network | |
| 10 | R107 Inverter | |
| 11 | R113 NAND/NOR Gate | |
| 1 | R121 | |
| 1 | R122 | |
| 6 | R123 Input Bus Gate | |
| 2 | R151 | |
| 17 | R202 Dual Flip Flop | |
| 5 | R203 Triple Flip Flop | |
| 5 | R205 Dual Flip Flop | |
| 3 | R302 Dual Delay (One Shot) | |
| 2 | R401 | |
| 1 | R405 Crystal Clock | |
| 1 | R581 | |
| 4 | R603 Triple Pulse Amplifier | |
| 1 | W500 | |
| 2 | W501 |