Differences

This shows you the differences between two versions of the page.

--- interrupt_scheduler [2016/05/31 22:57]
ex_writer [ACTINT]
+++ — (current)
@@ Line 1: / Line 1: @@
-====== Interrupt Scheduler ======
-The Interrupt Scheduler handles system timers and counters.
-===== Interrupt Scheduler Routines =====
-^ Name ^ Description ^
-| [[interrupt scheduler#actint|ACTINT]] | Activate automatic interrupt service (timers, music, blackout) |
-| [[interrupt scheduler#ctimer|CTIMER]] | Call custom timer |
-| [[interrupt scheduler#deccts|DECCTS]] | Decrement counters/timers under mask (used by ACTINT and DECCTS) |
-| [[interrupt scheduler#stimer|STIMER]] | Track and decrement game timers |
-===== Interrupt Scheduler Routine Descriptions =====
-==== ACTINT ====
-ACTIVE INTERRUPTS
-| Calling Sequence: | <code z80>SYSTEM    ACTINT</code> or <code z80>SYSSUK    ACTINT</code>|
-| Arguments: | None |
-| Outputs: | None |
-| Function: | Sets IM=2, INLIN=200, sets I register + INFBK\\ Calls TIMEX and TIMEY\\ Enables interrupts |
-| Description: | Once ACTINT is called, it provides interrupt service completely automatically by setting:\\   * Z80 Interrupt mode 2 (IM 2)  * INLIN = 200 (line 100)  * I register and Interrupt Feedback (INFBK)  * Enables interrupts (EI)\\ \\ It runs the seconds timer, the game timer, the music processor, and blackout timers, plus CT0, CT1, CT2, CT3. Timers function every 1/60th of a second. |
-==== CTIMER ====
-CUSTOM TIMER
-| Calling Sequence: | <code z80>CALL      CTIMER</code>|
-| Input: | HL = address of custom time base\\ B = value to load into time base 1 to 0 transition\\ C = counter mask as in [[interrupt scheduler#deccts|DECCTS]] |
-| Notes: | None |
-| Description: | HL is loaded and decremented. If HL != 0, then a return is executed, otherwise, HL is loaded with B and [[interrupt scheduler#deccts|DECCTS]] is called.\\ Registers HL, DE, BC, and AF are undefined upon exit. |
-| Restrictions: | None |
-==== DECCTS ====
-DECREMENT COUNTERS/TIMERS
-| Calling Sequence: | <code z80>SYSTEM    DECCTS</code> or <code z80>SYSSUK    DECCTS
-DB        (mask)</code>|
-| Arguments: | C = mask for which counters to decrement |
-| Outputs: | Sentry will notify the program |
-| Description: | Decrements counter if they are non-zero. If any counters go from 1 to 0, sentry is notified. |
-==== STIMER ====
-DECREMENT TIMERS
-| Calling Sequence: | <code z80>PUSH      AF
-PUSH      BC
-PUSH      DE
-PUSH      HL
-CALL      STIMER
-POP       HL
-POP       DE
-POP       BC
-POP       AF</code>|
-| Input: | None |
-| Description: | STIMER keeps track of game time. If it hits 0, then GSBEND bit in the game status byte is set. |
-| Uses: | AF, BC, DE, HL |
-| Calls: | Music processor on note (duration) expiration |
-| Note: | Sets bit 7 of KEYSEX to 1 on every second |