Cassette
The cassette input and output is based on square wave signals. The cassette out is generating a square wave signal by switching the Q flag between 0 and 1. The cassette input is linked to the EF2 flag.
Every bit is generated either by a high or low square tone to represent a 0 or 1. Where the start tone is a long square wave with a high tone, followed directly by all program data.
LOAD
First press 'B', then play and after that as soon as possible press the number of 'blocks of 256 bytes' you want to load (1 to F).
SAVE
First press the record button, then 'F' and the number of 'blocks of 256 bytes' you want to save (1 to F).