Assumptions Used in Digital Abstraction

In order to analyze and design digital circuits, a number of assumptions are made that underlie digital abstraction. It’s assumed that a circuit behaves in a ideal manner, allowing a designer to think in terms of 1s and 0s, without being concerned about the circuit’s electrical behavior and physical implementation.

There are five assumptions occasionally being made:

  1. All signals take on appropriate low and high voltages (their logic levels) representing discrete values 0 and 1. It imposes the physical circuit must not violate voltage level specifications in terms of component’s voltage threshold: VoH, VoL, ViH, ViL and noise margin;
  2. The current loads on circuit components are reasonable. An idealized component should be able to source or sink as much current at the output as its load requires without affecting the logic levels. It imposes the physical circuit must meet the static loading constraints in terms of component’s static load currents: IoH, IoL, IiH and IiL;
  3. All signals change between logic levels instantaneously. Due to component’s capacitive loading, the physical circuit must meet the propagation delay constraints when logic changes in terms of tpd;
  4. Wires are perfect conductors that propagate signals with no delay which means a change in the value of a signal at the output of a component is seen instantaneously at the input of other connected components. It imposes the circuit must guarantee its signal integrity due to parasitic load in wires;
  5. In a sequential circuit, a flip-flop stores the value of its data input at the moment the clock input changes (either edge-triggered or level-triggered) and the stored value is reflected on the output instantaneously. It imposes the circuit must meet timing constraint.

Activating Revision Control in Lyx

Lyx supports document revision control for collaborative document editing. It uses rcs, a gnu revision control system, for that purpose. You and your colleges then can register, checkout, merge and commit into your shared documents.

In Ubuntu Lucid, It was not installed by default when you installed Lyx package. So, you have to install rcs package using apt to enable Lyx revision control.

$> sudo aptitude install rcs

That’s it. You now can use revision control feature for your document. It is found at Lyx File menu.

First, register your document and than checkout it for editing.

Daftar IC Logika. Ada yang Mau Volunteer?

Ingin juga saya membuat daftar IC logika TTL/CMOS/BiCMOS seri 7400. Tapi, ini tentu saja akan memakan waktu lama. Saya ingin mendistribusikan pekerjaan ini ke mahasiswa saya yang mengambil kuliah Sistem Digital. Atribusi kontributor akan dicantumkan dalam pengantar, sebagai apresiasi atas bantuan pekerjaan. Dan tentu saja, tambahan point nilai (2) dan amal 🙂

Daftar IC tersebut sebenarnya sudah ada di wiki. Tujuan pekerjaan penulisan daftar ini adalah untuk memberikan deskripsi lebih lanjut dari IC tersebut dengan terstruktur, sehingga dapat digunakan lebih lanjut oleh siapa pun yang membutuhkan.

Penulisan daftar ini akan dibagi menjadi beberapa ‘keping’. Satu keping mengerjakan penulisan 3-4 buah IC seri 7400. Tiap seri IC memuat informasi berikut:

  • Seri dan fungsi logikanya serta atribut lainnya
  • Gambar diagram bloknya
  • Operasi logika dan tabel kebenaran/diagram pewaktuannya
  • Contoh IC berikut teknologi yang digunakan (TTL/CMOS/BiCMOS) dan linknya ke datasheetnya

Tiap keping dikerjakan oleh satu mahasiswa dan dituliskan ke dokumen (word, odt, pdf). Bagi mahasiswa R1 dan R2 Sistem Digital yang mau mengambil task ini, kirimkan email langsung ke saya. Pertanyaan dan lainnya silahkan isi komen atau kirim email.

Ayo, buruan 🙂

 

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