Atari 400 Technical Reference Manual page 167

Appendix C -- SID STATUS BYTE VALUES
Shown below are the known SIO STATUS BYTE hexadecimal values.
01 (001)
SA (13S)
SB
(139)
SC (140)
SE (142)
SF (143)
90 (144)
182
OPERATION COMPLETE (NO ERRORS)
DEVICE TIMEOUT (DOESN'T RESPOND)
DEVICE NAK
SERIAL BUS INPUT FRAMING ERROR
SERIAL BUS DATA FRAME OVERRUN ERROR
SERIAL BUS DATA FRAME CHECKSUM ERROR
DEVICE DONE ERROR
OPERATING SYSTEM C016555 -- Appendix C