IBM 5170 Technical Reference page 127

I
Command
I
Options
Set/Reset Command
A Set/Reset Mode Indicators command consists of two bytes.
~
The first is the command byte and has the following bit setup:
11101101 - hex ED
The second byte is an option byte. It has a list of the indicators to
be acted upon. The format of the option byte is as follows:
Bit 7
Reserved
Bit 6
Reserved
Bit 5
Reserved
Bit 4
Reserved
Bit 3 Reserved
~
Bit 2 Caps Lock indicator
Bit 1 Numeric Lock indicator
Bit 0
Scroll Lock indicator
Note: Bit 7 is the most-significant bit; bit 0 is the
least-significant.
The keyboard will respond to the Set/Reset Mode Indicators
command with an lACK
I ,
discontinue scanning, and wait for the
option byte. The keyboard will respond to the option byte with
an Ack, set the indicators, and continue scanning if the keyboard
was previously enabled.
If
another command is received in place
of the option byte, execution of the function of the Set/Reset
Mode Indicators command is stopped with no change to the
~ indicator states, and the new command is processed. Then
scanning is resumed.
Keyboard 4-9