rlm@117: 
rlm@117: (defn count-frames* []
rlm@117:   (-> (tick (mid-game))
rlm@117:       (IE! 0) ; disable interrupts
rlm@117:       (inject-item-assembly
rlm@117:        ;; write 00010000 to 0xFF00 to select joypad
rlm@117:        [0x18   ;D31D                    ; jump over          
rlm@117:         0x02   ;D31E                    ; the next 2 bytes
rlm@117:         0x00   ;D31F                    ; frame-count
rlm@117:         0x00   ;D320                    ; v-blank-prev
rlm@117: 
rlm@117:         
rlm@117:         0xFA   ;D321
rlm@117:         0x41   ;D322                    ; load (FF41) into A
rlm@117:         0xFF   ;D323                    ; this contains mode flags
rlm@117: 
rlm@117:         0x47   ;; copy A -> B
rlm@117:         
rlm@117:         0xCB
rlm@117:         0x3F ;; shift A right
rlm@117:         0x2F ;; complement A
rlm@117: 
rlm@117:         0xA0 ;; A & B -> A.
rlm@117:         0x47 ;; copy A -> B. Now the first bit of B is (VB == 1)
rlm@117:         
rlm@117:         0xFA
rlm@117:         0x20
rlm@117:         0xD3 ;; load v-blank-prev into A
rlm@117: 
rlm@117:         0xA0 ;; A & B -> A. 
rlm@117:         0x4F ;; copy A to C. Now C contains increment-counter?
rlm@117: 
rlm@117:         0xFA
rlm@117:         0x1F
rlm@117:         0xD3 ;; load frame-count into A
rlm@117: 
rlm@117:         0x81 ;; add increment-counter? to frame-count
rlm@117:         0xEA ;; store A into frame-count
rlm@117:         0x1F
rlm@117:         0xD3
rlm@117: 
rlm@117:         0x3E ;; load 1 into A
rlm@117:         0x01
rlm@117:         0xA0 ;; A & B -> A. Now A is (VB==1)
rlm@117:         0xEA ;; store A into v-blank-prev
rlm@117:         0x20
rlm@117:         0xD3
rlm@117: 
rlm@117:         0xC3   ;D348                   ; return to beginning
rlm@117:         0x1D   ;D349
rlm@117:         0xD3   ;D34A
rlm@117: 
rlm@117: 
rlm@117:         ])))