JiffyDOS NTSC fixes and screen blanking for transfer speedup

CONFIG.md

@@ -103,6 +103,10 @@ Adds support for the IEEC bus - for serial printers, disk drives, etc.
 
 Needs over 1000 bytes in KERNAL segment. If unsure - enable.
 
+### `CONFIG_IEC_BLANK_SCREEN`
+
+Causes screen blanking during some IEC operations (currently only JiffyDOS file loading) to increase the data transfer performance.
+
 ### `CONFIG_IEC_JIFFYDOS`
 
 Adds support for JiffyDOS fast protocol to the IEC bus.

c64/,,config_generic.s

@@ -41,6 +41,7 @@
 // I/O devices
 
 #define CONFIG_IEC
+#define CONFIG_IEC_BLANK_SCREEN
 #define CONFIG_IEC_JIFFYDOS
 // #define CONFIG_TAPE_NORMAL     // please keep disabled for now
 #define CONFIG_TAPE_TURBO

c64/,,config_mega65.s

@@ -43,6 +43,7 @@
 // I/O devices
 
 #define CONFIG_IEC
+#define CONFIG_IEC_BLANK_SCREEN
 #define CONFIG_IEC_JIFFYDOS
 // #define CONFIG_TAPE_NORMAL     // please keep disabled for now
 // #define CONFIG_TAPE_TURBO

c64/,,config_testing.s

@@ -42,6 +42,7 @@
 // I/O devices
 
 #define CONFIG_IEC
+// #define CONFIG_IEC_BLANK_SCREEN
 #define CONFIG_IEC_JIFFYDOS
 // #define CONFIG_TAPE_NORMAL     // please keep disabled for now
 #define CONFIG_TAPE_TURBO

c64/,,config_ultimate64.s

@@ -41,6 +41,7 @@
 // I/O devices
 
 #define CONFIG_IEC
+#define CONFIG_IEC_BLANK_SCREEN
 #define CONFIG_IEC_JIFFYDOS
 // #define CONFIG_TAPE_NORMAL     // please keep disabled for now
 #define CONFIG_TAPE_TURBO

c64/kernal/iec/iec_wait1ms.s

@@ -29,6 +29,8 @@ wait_x_bars: // additional entry point for tape support
 	dex
 	bne !-
 
+iec_wait_rts: // dummy RTS, for very short waits
+
 	rts
 
 

c64/kernal/iec_fast/load_jiffydos.s

@@ -3,8 +3,6 @@
 // JiffyDOS protocol support for IEC - optimized load loop
 //
 
-// XXX option does not work yet
-// #define CONFIG_IEC_BLANK_SCREEN
 
 #if CONFIG_IEC_JIFFYDOS && !CONFIG_MEMORY_MODEL_60K
 
@@ -61,6 +59,10 @@ load_jiffydos_loop:
 
 #if CONFIG_IEC_BLANK_SCREEN
 
+	// It JiffyDOS needs some time here; waste few cycles
+	nop
+	jsr iec_wait_rts
+
 	// Ask device to start sending bits
 	sta CIA2_PRA
 
@@ -87,8 +89,8 @@ load_jiffydos_loop:
 	lsr
 	lsr
 
-	// Wait for the drive - we have time to increment offset, cycles: 2
-	iny
+	// Delay, JiffyDOS needs some time, 2 cycles
+	nop
 
 	// Get bits, cycles: 4 + 2 + 2 = 8
 	ora CIA2_PRA                       // bits 2 and 3 on CLK/DATA
@@ -105,7 +107,8 @@ load_jiffydos_loop:
 	eor C3PO
 	eor CIA2_PRA                       // bits 6 and 7 on CLK/DATA
 
-	// Store retrieved byte, cycles: 6 
+	// Store retrieved byte, cycles: 2 + 6 = 8 
+	iny                                // NTSC needs this delay
 	sta (EAL),y                        // not compatible with CONFIG_MEMORY_MODEL_60K
 
 	// Retrieve status bits, cycles: 4