VT3XX

Introduction

The VT320 was an ANSI standard computer terminal introduced by DEC in 1987. The VT320 was the text-only version, while the VT330 added monochrome ReGIS, Sixel and Tektronix 4010/4014 graphics emulation. The VT340 added color; capable of displaying 16 colors from a palette of 4096 colors. The 300 series terminals replaced the earlier VT200 series, as a lower-cost system better able to compete with a number of VT220 clones that had entered the market. The VT300s introduced a number of new features compared to the VT200s. With the increase in RAM available, the 300s added the ability to store several pages of data locally, as well as perform editing on that data entirely within the terminal. Up to 19,008 characters could be stored in 1 to 6 pages of internal RAM.

The user could scroll up and down among several pages, normally about three, perform edits, and then send all of the changes to the host in a single operation. This required compatible host-side software to work. That memory also meant all of the 300 series were able to store large numbers of sixel-based glyphs, allowing them to be used not only as a user-defined character set as in the earlier 200s, but also to produce full-screen bitmap graphics by storing a separate sixel for each location on the screen.

All members of the VT3XX line could support two sessions, either using two MMJ ports available on some models, or in the case of the VT330 and VT340, using a single serial connection using a system known as TD/SMP on the server and SSU on the terminals. The TD/SMP protocol was never published, and only worked with DEC's own terminal servers. Using either system, the terminal could display the two sessions "stacked" and switch between them, or by splitting the screen vertically to show them one above the other, or horizontally side-by-side. The serial ports could run up to 19.2 Kbps, the same maximum rate as the VT200s. The screen itself was a 14-inch CRT mounted on a tilt and swivel stand. It offered a resolution of 800 by 480, and a number of different glyphs could be used to produce 25 lines or either 80 or 132 columns of text, the 25th line normally being used to display status codes, like caps lock, generated locally in the terminal. The VT330 had two bit-planes that produced 4 shades of gray, while the VT340 had four bit-planes to produce 16 colors out of a palette of 4096.

Compatibility Modes

• VT200 mode, 7-bit controls
• VT200 mode, 8-bit controls
• VT100 mode
• VT52 mode
• Tektronix 4010/4014 mode