ZX81/TS 1000 Tips

Here is a little function, which may be placed at the beginning or within a machine code program, to stop the program until the tape player starts inputting data.

XXXX  DBFE       HOLD: IN A,(FE)
      CB7F             BIT 7,A
      28FA             JR Z, HOLD

Where XXXX represents the address.

This is a routine to set RAMTOP and then install your machine code above it. As an example, let’s say that you have 80 bytes of machines code in 1 REM and you want to install it as address 20000 [7530 hex].