Tandy 1000 SL Technical Reference Manual page 544

BIOS Services
Get Current Comm Status
Read the communication status into AX.
Entry Conditions
AH
=
3
DX
=
port number (0 or 1)
Exit Conditions
AH
=
RS-232Cstatus, as follows (set
=
true):
Bit0
=
data ready
Bit 1
=
overrun error
Bit 2
=
parity error
Bit3
=
framingerror
Bit4
=
breakdetect
Bit 5
=
transmitter holding register empty
Bit 6
=
transmitter shift register empty
Bit 7
=
timeout occurred
AL
=
modem status, as follows (set
=
true):
Bit 0
=
delta clear to send
Bit 1
=
delta data set ready
Bit 2
=
trailing edge ring detector
Bit 3
=
delta receive line signal detect
Bit4
=
clear to send
Bit 5
=
data set ready
Bit 6
=
ring indicator
Bit 7
=
receive line signal detect
23.