PC 1401 Resources

More info: Simon-Lehmayr.de (english version)

Errors

From the hard cover:

Code	Meaning
1	Syntax error
2	Calculation error
3	Illegal function argument (Usually type error)
4	Too large a line number (Line number is too large / Too many lines in RAM)
5	NEXT without FOR or RETURN without GOSUB (Stack underflow)
6	Memory overflow (Usually a stack overflow)
7	PRINT USING error (I don't know what this one even means)
8	I/O device error (Usually a communication error)
9	Other errors

Mnemonics can be found on the website linked above. I have a few additional remarks:

You can use POKE &8800,... to write the program to RAM in a usually-free region.
It can be called using CALL &8800
Ports on PC-1401 are different in ways I have not yet discovered. The 11-pin IF cannot be controlled using any of the known methods.
On the PC-1403, PORT F is very easy to control and will not get reset by the BASIC interpreter.
The CSAVE/XOUT pin gets pulled high for a short moment upon RUN.
The CPU uses INSTRUCTION,VALUE,... order and is Big-Endian.
To write to memory, use LIA,value,LIP,address,EXAM for address < 128 and LIA,value,LIDP,addresshigh,addresslow,STD for larger addresses
RTN will return to the BASIC interpreter as expected.

REM Program to output 1 @ pin 4 on PC-1403
REM LIA,255,LIP,95,EXAM,OUTF,RTN
POKE &8800,2,255,18,94,219,95,55
CALL &8800
END