Specification: 8-bit Up-Counter

Purpose: Minimal block to demonstrate the specification → RTL flow in Module 1.

How to Read This Spec (Beginners)

If you are new to reading hardware specs, use this document in order:

Interface (Section 2) — Tells you every port: name, direction (input/output), and width. This becomes your module’s port list in RTL.
Behavior (Section 3) — Tells you what happens on reset, when to increment, and when to hold. This becomes the logic inside an always block (reset first, then enable, then hold).
Timing (Section 4) — Tells you that everything is synchronous to the positive edge of clk. That tells you to use always @(posedge clk) and no combinational logic for the counter output.

For a step-by-step guide on understanding any spec, see module1/UNDERSTANDING_THE_SPEC.md.
For translating this spec into RTL, see module1/SPEC_TO_RTL_GUIDE.md and WALKTHROUGH.md.

Block name: counter
Function: 8-bit up-counter with synchronous reset and enable. Counts from 0 to 255 and wraps to 0.

Port	Direction	Width	Description
`clk`	input	1	Clock; positive edge is active.
`rst_n`	input	1	Active-low synchronous reset.
`enable`	input	1	When high, counter increments on the next clk.
`count`	output	8	Current count value (0–255).

Reset: On the rising edge of clk, if rst_n is low, count is set to 8'h00 and remains until rst_n goes high.
Count: On the rising edge of clk, if rst_n is high and enable is high, count increments by 1. If count is 255, the next increment wraps to 0.
Hold: If enable is low (and not in reset), count does not change.

All behavior is synchronous to the positive edge of clk.
No multi-cycle or combinational paths are specified; implementation is single-cycle update.

This spec is intentionally small so that:

Spec → RTL: You can map each requirement to RTL (reset, enable, increment, width).
Verification: A simple testbench can drive clk/reset/enable and check that count matches expectations (e.g., after N enabled cycles, count = N mod 256).
Methodology: The same flow (spec → RTL → testbench) applies to UART, SPI, and I²C in later modules.