enable weak pull-up at reset line to console if low-active is detected

Some CPUs (especially those in Twin Famicoms) seems to not have an internal weak pull-up (WPU). Without the PICs WPU, one has to reset the console once to get the console running. This commit resolves that issue. Thank you to voultar (Assemblergames forum user) and to Zachary for reporting and testing!
borti4938 · Feb 27, 2016 · 6e478129b5cfa9a209ac8781f8fe4260d0d1926d · 6e47812
1 parent bde843e
commit 6e478129b5cfa9a209ac8781f8fe4260d0d1926d
Unified Split

Showing with 17 additions and 1 deletion.

+9 −1 NES/IGR_for_NESRGB/normal version/nesrgb_igr_684.asm

+8 −0 NES/IGR_for_NESRGB/risky version/nesrgb_igr_684_risky.asm
diff --git a/NES/IGR_for_NESRGB/normal version/nesrgb_igr_684.asm b/NES/IGR_for_NESRGB/normal version/nesrgb_igr_684.asm
@@ -753,8 +753,16 @@ detect_reset_type
    btfss   PORTA, RESET_IN         ; jump next instruction for low-active reset
    movwf   reg_reset_type
+  
+lowreset_cpu_help
+  
+    skipnext_for_lowreset
+  
+    goto    set_led_type
+  
+    banksel TRISA
+  
+    M_movlf 1<<RESET_OUT, WPUA
+  
+    bcf	    OPTION_REG, NOT_RAPU    ; enable global pull-up
+  
+    banksel PORTA
+  
+
 set_led_type
-  
-    call    setleds ; set LEDs according to teh LED type
+  
+    call    setleds ; set LEDs according to the LED type
 init_end
    clrf    reg_ctrl_reset  ; clear this reg here just in case

diff --git a/NES/IGR_for_NESRGB/risky version/nesrgb_igr_684_risky.asm b/NES/IGR_for_NESRGB/risky version/nesrgb_igr_684_risky.asm
@@ -771,6 +771,14 @@ detect_reset_type
    btfss   PORTA, RESET_IN         ; jump next instruction for low-active reset
    movwf   reg_reset_type
+  
+lowreset_cpu_help
+  
+    skipnext_for_lowreset
+  
+    goto    set_led_type
+  
+    banksel TRISA
+  
+    M_movlf 1<<RESET_OUT, WPUA
+  
+    bcf	    OPTION_REG, NOT_RAPU    ; enable global pull-up
+  
+    banksel PORTA
+  
+
 set_led_type
    call    setleds ; set LEDs according to teh LED type