The Cricket! uses a 4.9152MHz crystal which it uses to derive the
frequency of the PSGs resulting in 20% higher timer values. The note
values were extracted from the Appendix C of the Cricket! manual.
This version requires the Cricket! from Street Electronics to be
connected on the serial port 2 of the Apple //c. It uses the VBL
interrupt to replace the 60Hz Interrupts of the Mockingboard version so
it will run a bit slower on european models with 50Hz. This can be
partly compensated by selecting a lower TEMPO value, even tough it is
not the perfect solution yet.
* AY register buffer moved from $300 to $8400. Replaced fixed
references with an EQU.
* Song moved from $4000 to $8900. This allows to keep the whole player
routine including buffers and songs between $8400 and $9200.
* Changed zero page pointers to safer locations.
The Mockingboard Developer’s Toolkit included as interrupt based MCS
player that was obviously based on the original sources but included
important corrections. This included the PSG initialization and a
correction the frequency tables.
The code was moved to the address $8500 to match that implementation.
