The machine used a 12 digit display (8 LED anodes scanned by an Anode driver, and 12 `digits` scanned by a Cathode driver, the latter being used also to scan the keyboard`s 7 columns. The bus is also simplified : 4 lines : the clock`s 2 phases, the Sync line and a new line names Isa multiplexing addresses and data on the system time word.
Click here to download the full size of the above Circuit.
The Power on logic is also included in the ACT and only a few analog elements (4 resistors - only 2 are shown on the HP sketch, 2 capacitors, 1 inductor) are needed along with the 5 chips : ACT (PMOS), ROM1 (PMOS), RAM (PMOS) ROM0 and Anode driver (PMOS) and Cathode driver (bipolar). Note that there is -this time- no big help like the US Patent 4, 001, 5692, for the HP-45 (with an object and source ROM listing, keyed in by Eric Smith in 1995). There are 2 patents related to the HP-25, one is #3, 987, 290, 0ct 19, 1976, granted to Peter D. Dickinson for a "Calculator apparatus for displaying data in engineering notation", the other is #4, 177, 520 for a `Calculator apparatus having a single-step key for displaying and executing program steps and displaying the result`, granted to Randall B. Neff. Two previous study were priceless. Tom NAPIER described back in 1978 the machine time word of the HP-67 (the Woodstock Masterpiece) and commented part of the ROM, and Eric SMITH wrote `NonPareil` a ROM image emulator for the Classic and Woodstock. The HP 25 and Woodstock instruction set is not completely new. In fact, it is an extension of the HP-35`s set. It is now completly deciphered and I wrote emulator of the HP-67 is running faithfully the ROM image code (with the operations of the card reader). But sometimes big differences appear driven by the fast pace of technology evolution. As a result of the integration level progress,...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: