---
title: "A Z80 machine language program to use the ZX81 as an audio frequency counter"
type: "article"
slug: "a-z80-machine-language-program-to-use-the-zx81-as-an-audio-frequency-counter"
url: "http://localhost/article/a-z80-machine-language-program-to-use-the-zx81-as-an-audio-frequency-counter/"
markdown_url: "http://localhost/article/a-z80-machine-language-program-to-use-the-zx81-as-an-audio-frequency-counter.md"
published_at: "2020-10-27T21:13:07+00:00"
modified_at: "2024-05-26T14:34:01+00:00"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
category:
  - name: "QZX"
    slug: "qzx"
    taxonomy: "category"
    url: "http://localhost/category/periodicals/qzx/"
post_tag:
  - name: "Machine language programming"
    slug: "machine-language"
    taxonomy: "post_tag"
    url: "http://localhost/tag/machine-language/"
  - name: "TS 1000"
    slug: "ts1000"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts1000/"
  - name: "Type-in program"
    slug: "type-in-program"
    taxonomy: "post_tag"
    url: "http://localhost/tag/type-in-program/"
  - name: "ZX81"
    slug: "zx81"
    taxonomy: "post_tag"
    url: "http://localhost/tag/zx81/"
model:
  - name: "Sinclair ZX81"
    slug: "zx81"
    taxonomy: "model"
    url: "http://localhost/model/zx81/"
  - name: "Timex/Sinclair 1000"
    slug: "ts-1000"
    taxonomy: "model"
    url: "http://localhost/model/ts-1000/"
indiv:
  - name: "Carol F. Milazzo (KP4MD)"
    slug: "carol-f-milazzo"
    taxonomy: "indiv"
    url: "http://localhost/indiv/carol-f-milazzo/"
publication: "QZX"
publication_r:
  id: 21219
  title: "QZX"
  type: "periodical"
  url: "http://localhost/periodical/qzx/"
authors: "Carol F. Milazzo"
volume: "2"
issue: "11"
issues_articles:
  - id: 49028
    title: "QZX v2 n11"
    type: "issue"
    url: "http://localhost/issue/qzx-v2-n11/"
pubdate: "October 1984"
archive_link: false
volumeissue: "v2n11"
---

# A Z80 machine language program to use the ZX81 as an audio frequency counter