VT52

The VT52 was a very popular video terminal by DEC, introduced 1975. The CRT displays 24 lines of 80 characters in both upper and lower case.

VT52 terminal

It uses a custom processor built from TTL parts to execute 1024 words of 8-bit wide microcode. The data path is 7 bits wide, as is the 2048-word RAM. The predecessor VT50 is almost identical, except there is only 512 words of microcode, 1024 words of RAM, the CRT display 12 lines, and text is upper case only.

A VT52-compatible terminal emulator was used in the Atari TOS operating system.

Escape sequences

Due to its popularity, the VT52 escape sequences became a de facto standard for microcomputers for a while, before VT100 and ANSI took over.

Name	Sequence	Description
Line Feed	LF	Move cursor down. On last line, scroll text up.
Cursor Down	ESC B	Move cursor down. On last line, do not scroll.
Reverse Line Feed	ESC I	Move cursor up. On first line, scroll text down.
Cursor Up	ESC A	Move cursor up. On first line, do not scroll.
Cursor Right	ESC C	Move cursor right. On last column, stay there.
Cursor Left	ESC D, or BS	Move cursor left. On first column, stay there.
Home	ESC H	Move cursor to top line, first column.
Carriage Return	CR	More cursor to first column.
	TAB	Move cursor to next tab stop.
Direct Cursor Addressing	ESC Y <line> <column>	Move cursor.
Erase to End of Line	ESC K	Erase from cursor position to end of line.
Erase to End of of Screen	ESC J	Erase from cursor position to end of screen.
Ring the Bell	BEL	Sound the buzzer
Identify Terminal Type	ESC Z	Respond e.g. "ESC K" for a plain VT52.
Enter Hold Screen Mode	ESC [
Exit Hold Screen Mode	ESC \
Enter Alternate Keypad Mode	ESC =
Exit Alternate Keypad Mode	ESC >
Enter Graphics Mode	ESC F
Exit Graphics Mode	ESC G
Extensions from Digital Research
Erase and Home	ESC E	Erase screen and move cursor to top line, first column.
Erase Current Line	ESC l
Erase to Beginning of Line	ESC o
Erase to Beginning of Screen	ESC d
Insert Line	ESC L
Save Cursor Position	ESC j
Restore Cursor Position	ESC k
Reverse Video	ESC p
Normal Video	ESC q
Set Foreground Color	ESC b <color>
Set Background Color	ESC c <color>
Enable Cursor	ESC e
Disable Cursor	ESC d
Enable Line Wrap	ESC v
Disable Line Wrap	ESC w

External links

• VT52 - documentation at Bitsavers
  • DECscope Users' Manual (EK-VT5X-OP-001)
  • VT52 DECscope Maintenance Manual (EK-VT52-MM-002)
  • VT52 Field Maintenance Print Set (MP00035)
• Microcode ROM images
• Character generator ROM image
• VT52 hardware simulation