Difference between revisions of "Signetics 2513"

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Revision as of 17:00, 19 September 2022

The Signetics 2513N.

The Signetics 2513 is a character generator developed by Signetics which displays characters on a display screen and was used as the video chip for several early 8-bit devices. The default character set supports uppercase letters, numbers, and some punctuation and mathematics symbols.

Personal

I learned about the Signetics 2513 while reading about the Apple I.

Technical

The chip can display 40×24 characters on a screen and store 64 monochrome bitmaps, each with a resolution of 8×5 pixels, in its ROM. These bitmaps cannot be changed, However, for a fee, the company allowed customers to mail in their own bitmaps and they would mail them ROM chips loaded with their custom characters. The chip was sold in two packages: silicon or ceramic, signified N and I respectively, both in a DIP.

Devices

Characters

The 2513 could only store 64 characters, so it couldn't fit the entire ASCII table, but it could still convey most of the table, since 33 of the ASCII character set is non-printable, and lowercase letters make up another 26. The order of the characters is similar to ASCII, but with the structure moved around to fit into only 64 slots.

0 1 2 3 4 5 6 7 8 9 A B C D E F
0x @ A B C D E F G H I J K L M N O
1x P Q R S T U V W X Y Z [ \ ] ^ _
2x  ! " # $  % & ' ( ) * + , - . /
3x 0 1 2 3 4 5 6 7 8 9  :  ; < = >  ?

Each unique character set ROM had a unique model number, with the default being CM2140. It looks like this when rendered:

File:Signetics 2513 - Characters.png

Signetics also sold a special ROM for Japanese customers, model number CM4800, which had a nearly complete katakana set.

Media

Documentation

Links