Fix D2 to read the entire SRAM content

Allow to read up to 0x21ff, which is the last byte of SRAM.  Set default
starting address to 0x200, which is the first true byte.

0x0-200 is mapped to register/io space and could cause issues when read
from bi-directional registers.

Firmware/Dcodes.cpp

@@ -246,32 +246,31 @@ void dcode_1()
     ### D2 - Read/Write RAM <a href="https://reprap.org/wiki/G-code#D2:_Read.2FWrite_RAM">D3: Read/Write RAM</a>
     This command can be used without any additional parameters. It will read the entire RAM.
     #### Usage
-    
+
         D2 [ A | C | X ]
-    
+
     #### Parameters
-    - `A` - Address (x0000-x1fff)
-    - `C` - Count (1-8192)
+    - `A` - Address (x0000-x21ff)
+    - `C` - Count (1-8704)
     - `X` - Data
 
 	#### Notes
 	- The hex address needs to be lowercase without the 0 before the x
-	- Count is decimal 
+	- Count is decimal
 	- The hex data needs to be lowercase
-	
+
     */
 void dcode_2()
 {
-	LOG("D2 - Read/Write RAM\n");
-	uint16_t address = 0x0000; //default 0x0000
-	uint16_t count = 0x2000; //default 0x2000 (entire ram)
-	if (code_seen('A')) // Address (0x0000-0x1fff)
+	DBG(_N("D2 - Read/Write RAM\n"));
+	uint16_t address = 0x200; // default to start of sram
+	uint16_t count = 0x2200; // entire addressable space
+	if (code_seen('A')) // Address (0x0000-0x21ff)
 		address = (strchr_pointer[1] == 'x')?strtol(strchr_pointer + 2, 0, 16):(int)code_value();
-	if (code_seen('C')) // Count (0x0001-0x2000)
+	if (code_seen('C')) // Count (0x0000-0x2200)
 		count = (int)code_value();
-	address &= 0x1fff;
-	if (count > 0x2000) count = 0x2000;
-	if ((address + count) > 0x2000) count = 0x2000 - address;
+	if (address > 0x2200) address = 0x2200;
+	if ((address + count) > 0x2200) count = 0x2200 - address;
 	if (code_seen('X')) // Data
 	{
 		uint8_t data[16];
@@ -280,7 +279,7 @@ void dcode_2()
 		{
 			for (uint16_t i = 0; i < count; i++)
 				*((uint8_t*)(address + i)) =  data[i];
-			LOG("%d bytes written to RAM at address %04x", count, address);
+			DBG(_N("%d bytes written to RAM at address 0x%04x\n"), count, address);
 		}
 		else
 			count = 0;