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Asked: 2026-06-15T04:09:23+00:00

I’m implementing a vt100 terminal emulator in javascript and the vt100 spec (from man

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I’m implementing a vt100 terminal emulator in javascript and the vt100 spec (from man terminfo and infocmp) tells me that smkx=\E[?1h\E= is the code to enter key-board transmit mode and rmkx=\E[?1l\E> is the code to leave ‘key-board transmit’ mode. I couldn’t really understand what key-board transmit mode is.

From http://vt100.net/dec/ek-vt220-tm-001.pdf,

7.4.4.1 Keyboard Transmit Mode — The keyboard codes and a few other special codes are transmitted via a serial line output in PORT of the
8051. The transmitted signal goes from the 8051 to a driver, through the keyboard cable, monitor and video cable to the CPU. A UART within
the 8051 controls the transmission”

I’m getting these codes while entering into and leaving vim, respectively. Can I safely ignore these codes or do I need to handle them? In the latter case, what am I supposed to do?

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1 Answer

  1. Editorial Team

    These two strings contain two sequences each; they control subtly different things:

    The first of these,

    CSI ? 1h
CSI ? 1l

    controls DEC private mode number 1, DECCKM, cursor key mode. This mode determines whether the four arrow keys (Up, Down, Left, Right) will send SS3 or CSI-prefixed sequences.

    The second pair of sequences,

    ESC =
ESC >

    are called DECKPAM, keypad application mode, and DECKPNM, keypad numeric mode. This determines whether the number keypad sends control sequences, or normal numbers (i.e. consider it similar to the Numlock feature).

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