Assembly Program Loader to RAM Simulator

Fig. 1 — Assembly Program Loader to RAMInteractive simulation

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What You'll Learn

Trace loader address and data outputs to the corresponding RAM inputs.
Explain why one rising edge writes one compiled byte.
Verify the exact eight-byte sequence stored at addresses 0 through 7.
Distinguish CS, WE, and OE roles in the saved topology.
Recognize that no decoder, manual address bank, or visible RAM data output is present.

How It Works

The ASSEMBLY_PROGRAM_LOADER is connected directly to a 256-word × 8-bit RAM. Loader outputs 0–7 drive RAM address bits A0–A7, outputs 8–15 drive data inputs D0–D7, and loader control outputs drive RAM WE and CS. The same clock reaches both components.

Opening the loader and choosing its load action sets the current address and instruction index to 0. While the shared loader-enable switch is high, the loader drives address and data and asserts CS and WE. Each rising edge writes one byte into RAM, then advances to the next address. The compiled binary is 10 4F 21 75 61 60 60 60 (hex), so eight write edges fill addresses 0 through 7.

When all bytes have been processed, the loader marks the operation complete, releases its address/data outputs, and deasserts CS and WE. RAM OE is driven by the second switch, but with CS low the RAM outputs remain high-Z. Those outputs are not connected to any visible indicator. This is a loader-to-memory write demonstration, not a manually addressed RAM or decoder circuit.

Try It Step-by-Step

Set the listed controls in the embedded circuit, then compare the observed modeled state with the expected result.

1
Clock=stopped lowLoader action=Load ProgramLoader enable / address OE / data OE=1RAM OE=1
Expected:The loader presents address 0 and byte 0x10 with loading controls asserted
What you'll see:Open the loader, start loading the already compiled program, hold the loader-enable switch at 1, and pause CLK low before the first edge.
2
Clock=1 rising edgeLoader enable / address OE / data OE=1
Expected:RAM[0] = 0x10; the loader advances to address 1 and byte 0x4F
What you'll see:Apply one rising edge. RAM address 0 receives 0x10; the loader advances to address 1 and prepares 0x4F.
3
Clock=7 additional rising edgesLoader enable / address OE / data OE=1
Expected:RAM[0..7] = 10 4F 21 75 61 60 60 60 (hex), and loading completes
What you'll see:Apply seven more rising edges. Inspect RAM addresses 0–7 and confirm the exact hexadecimal sequence; the loader then reports completion.
4
Clock=stopped after load completionRAM OE=1
Expected:The loader releases address/data, CS and WE are low, and RAM data outputs are high-Z
What you'll see:After completion, inspect the nets with RAM OE still high. Loader CS is low, so RAM is not in read mode and its unconnected outputs remain high-Z.

Components Used

Control Switch

×2

Role: One switch enables loading plus address/data drive; the other drives RAM output enable.

Clock

×1

Role: Provides the rising edges that advance the loader and synchronously write RAM.

RAM

×1

Role: Stores 256 eight-bit words; the loader is wired to addresses, data inputs, CS, WE, and CLK.

Assembly Program Loader

×1

Role: Compiles/stores the preset eight-byte program and drives address, data, CS, and WE while a load is active.

Applications and Design Context

Program-memory initialization. A loader can translate source into bytes and write a memory image before execution begins.

Boot and test workflows. Clocked loading provides an observable sequence of address, data, and write-control transactions.

Memory-interface education. The circuit separates synchronous write control from high-impedance read behavior.

Assembler verification. Inspecting emitted bytes helps validate the actual binary independently of descriptive source comments.

Frequently Asked Questions

Is an external address decoder present?

No. The production circuit contains one assembly program loader, one 256×8 RAM, one clock, and two control switches. There is no DECODER component or bank of manual address switches.

What do the two switches control?

The first switch fans out to the loader's LOAD, address-output-enable, and data-output-enable inputs. It must be high while loading. The second switch drives RAM OE, but OE cannot produce a read while loader-driven CS is low after completion.

What data is loaded?

The saved loader binary is eight bytes: 10 4F 21 75 61 60 60 60 in hexadecimal. Because the saved source text and serialized mnemonic metadata do not agree, this page describes the executable bytes rather than inventing instruction meanings.

When does RAM write?

While loading, the loader drives an eight-bit address, an eight-bit data byte, CS, and WE. On each rising clock edge, RAM writes the current byte because both CS and WE are high.

Where are results visible?

The circuit has no lights or displays. Inspect the loader's progress/memory map and the RAM component state. The RAM data outputs are otherwise unconnected.