Assembly Language: How to Make Sounds example

This code example provides a set of keyboard routines to control sound output while waiting for a user to enter a keyboard character. The advantage to this method is that a main routine can call these sound routines to play a sound sequence, and the sound routines will return control back to the main routine whenever the user enters keyboard data so that the main routine can continue computing while the sound plays in the background. The code example has two different code entry points for getting keyboard data. One code entry point is a standard get_keyinput call which will wait for a key and update the sound data until a key code is found. The other code entry point is the get_keyinput_to call, which will wait a set amount of time for a key code and if none is found, return with a no key code found condition. The calling routine puts a timeout counter value in register AX on entry. The counter value is based on the system clock which ticks at 18.2 times per second. The entry point start_table_sound is used to begin a background sound sequence. On entry, the register BX indexes a table of sound data. The table has a format of four byte entries and is terminated by a data word of zero. The four bytes are used as two words: the first is a duration count and the second is a tone value. There are two code entry points for turning the background sound off and on. There is also a utility to flush out the keyboard buffer that can be executed with a call to flush_keyboard. Continue reading “Assembly Language: How to Make Sounds example”