# HG changeset patch
# User Robert McIntyre <rlm@mit.edu>
# Date 1334165731 18000
# Node ID f86bd04bd9fc4f424140163c9f07174eebbde0ce
# Parent  5c4a30521d099ddab93b998ab6d843d2a4cfe15c
simplifying frame-metronome

diff -r 5c4a30521d09 -r f86bd04bd9fc clojure/com/aurellem/gb/rlm_assembly.clj
--- a/clojure/com/aurellem/gb/rlm_assembly.clj	Wed Apr 11 11:43:51 2012 -0500
+++ b/clojure/com/aurellem/gb/rlm_assembly.clj	Wed Apr 11 12:35:31 2012 -0500
@@ -64,7 +64,8 @@
     (+ 256 n) n))
 
 (defn frame-metronome []
-  (let [timing-loop
+  (let [init [0x06 155] ;; init B to out of LY range
+        timing-loop
         [0x47    ;; A->B
          
          0x26 
@@ -76,36 +77,44 @@
          0x2C
 
          0x7E]   ;; (HL) -> A, now A = LY (vertical line coord)
-        jump-if-not-144
-        [0xFE
-         144     ;; compare LY (in A) with 144
-         0x20    ;; jump back to beginning if LY != 144 (not-v-blank)
-         (->signed-8-bit (+ -4 (- (count timing-loop))))]
         continue-if-different
         [0xB8    ;; compare A with B
          0x28
          (->signed-8-bit
-          (+ -3 (- (+ (count timing-loop) (count jump-if-not-144)))))]]
-    (concat timing-loop jump-if-not-144 continue-if-different)))
+          (+ -3 (- (count timing-loop))))
+         ]
+        continue-if-144
+        [0xFE
+         144     ;; compare LY (in A) with 144
+         0x20    ;; jump back to beginning if LY != 144 (not-v-blank)
+         (->signed-8-bit
+          (+ -4 (- (count timing-loop))
+             (- (count continue-if-different))))]]
 
-(defn test-frame-metronome []
-  (let [inc-C [0x0C 0x18
-               (->signed-8-bit
-                (+ -3 (- (count (frame-metronome)))))]
-        program (concat (frame-metronome) inc-C)
-        count-frames
-        (-> (tick (mid-game))
-            (IE! 0)
-            (BC! 0)
-            (set-memory-range pokemon-list-start program)
-            (PC! pokemon-list-start))
-        steps 151]
-    (assert
-     (= 151
-        (C (run-moves count-frames (repeat steps [])))))
-    count-frames))
+    (concat init timing-loop continue-if-different continue-if-144)))
 
 
+(defn test-frame-metronome
+  "Ensure that frame-metronome ticks exactly once every frame."
+  ([] (test-frame-metronome 151))
+  ([steps]
+     (let [inc-C [0x0C 0x18
+                  (->signed-8-bit
+                   (+ -3 (- (count (frame-metronome)))))]
+           program (concat (frame-metronome) inc-C)
+           count-frames
+           (-> (tick (mid-game))
+               (IE! 0)
+               (BC! 0)
+               (set-memory-range pokemon-list-start program)
+               (PC! pokemon-list-start))
+           C-after-moves (C (run-moves count-frames (repeat steps [])))]
+       (println "C:" C-after-moves)
+       (assert (= steps C-after-moves))
+
+       (println "C =" steps "after" steps "steps")
+       count-frames)))
+
 (defn main-bootstrap-program [start-address]
   (let [[start-high start-low] (disect-bytes-2 start-address)
         ]