IBM 5170 Technical Reference page 60

RAM
lID
the System Board
Manufacturing Mode
Display Type
Keyboard Inhibited
Data
Bus
o
U
T
I---~P
U
System Reset
Gate A20
+
Output Buffer Full ---.
+
Input Buffer Empty------.
Keyboard Clock
-,------1- ­
T Keyboard Data
--r--,r-J-­
r-------1._~TO 1-4--------..1
'---------' T l I - 4 - - - - - - - - - '
Status Register
The status register is an 8-bit read-only register at I/O address
hex 64.
It
has information about the state of the keyboard
controller (8042) and interface.
It
may be read at any time.
Status-Register Bit Definition
Bit 0 Output Buffer Full-A 0 indicates that the keyboard
controller's output buffer has no data. A
1
indicates that
the controller has placed data into its output buffer but
the system has not yet read the data. When the system
reads the output buffer (I/O address hex 60), this bit
will
return to a O.
Bit 1 Input Buffer FuU-A 0 indicates that the keyboard
controller's input buffer (I/O address hex 60 or 64) is
1-38 System Board