GD-77 CODEPLUG MAP, VALID FOR FIRMWARE V2.6.3
(but should be fairly accurate for older/newer versions too)

Address in HEX and DECIMAL with first byte of codeplug and/or default.dat being addr 0:

Address
Hex	Decimal		Use
00-07	00-07		8 bytes to identify file as a GD-77 compatible configuration.  Must be set to "MD-760" followed by 
			two hex FF bytes.

08-7F			Spare?  Filled with FF (120 bytes)

80,81	128,129		Lower UHF freq.  Change to hex bytes 94 & 01 to set lowest freq as 194 MHz
82,83	130,131		Upper UHF freq.  Change to hex bytes 20 & 05 to set upper freq as 520 MHz

84,85	132,133		Lower VHF freq.  Change to hex bytes 30 & 01 to set lowest freq as 130 MHz
86,87	134,135		Upper VHF freq.  Change to hex bytes 01 & 78 to set upper freq as 178 MHz

88-8D	136-141		Last programmed time encoded as hex bytes eg: 20 17 09 09 08 15 is 9th Sept 2017 8:15am

8E			Spare?  Filled with $FF

8F			Spare?  Filled with $FF

90-97	144-151		Radio type displayed under Dev Info, encoded as ASCII. Default reads "GD-77"

98-A7	152-167		Radio serial number displayed under Dev Info, encoded as ASCII (last digit scrolls off screen)
			16 digits available, but GD-77 serials are only 10 digits.  Unused bytes = FF. Default is empty.

A8-AF	168-175		Radio CPS version displayed under Dev Info, encoded as ASCII.  Default is empty

B0-B7	176-183		Radio H (hardware) version displayed under Dev Info, encoded as ASCII.  Default is empty.
			(I changed mine to read HWver3.1, which is what is printed on the PCBs of my GD-77)

B8-BF	184-191		Radio soft version (firmware) displayed under Dev Info, encoded as ASCII.

C0-D1	192-209		DMR DSP version displayed under Dev Info, encoded as ASCII.  Default is "HRC6000 V1.2.6"

D2-D7			Spare?  Filled with $FF (6 bytes) - can't be changed by hexedit, radio or CPS re-writes back to $FF

D8-DF			Spare?  Filled with $00 (8 bytes)

E0-E7	224-231		Radio name in ASCII

E8-EB	232-235		DMR radio ID

EC-F0			Spare?  Filled with $00 (5 bytes)

F1	241		General settings: TX preamble in steps

F2	242		General settings: Monitor type, 00=open, 01=silent.

F3	243		General settings: VOX sensitivity as hex

F4	244		General settings: RX low battery interval in steps

F5	245		General settings: Call alert tone duration in steps

F6	246		General settings: Lone worker resonse timer in steps

F7	247		General settings: Lone worker reminder timer in steps

F8	248		General settings: Talkaround private call hang time in steps

F9	249		General settings: Talkaround group call hang time in steps

FA	250		General settings: 	bit 8 set = ARTS always
						bit 7 set = ARTS once
						bit 6 set = Unused?
						bit 5 set = Unused?
						bit 4 set = Unfamiliar number tone
						bit 3 set = Reset tone
						bit 2 set = Unused?
						bit 1 set = Unused?

FB	251		General settings: 	bit 8 (MSB) = Battery saver preamble
						bit 7 set = Battery saver receive
						bit 6 set = Disable all tone
						bit 5 set = Unknown function???
						bit 4 set = Channel free indication tone
						bit 3 set = Self test pass tone
						bit 2 set = Analog talk permit tone
						bit 1 set = Digital talk permit tone

FC	252		General settings: 	bit 8 (MSB) set = private call
						bit 7 set = TX inhibit quick key override
						bit 6 set = disable all LED
						bit 5 set = Unused?
						bit 4 set = Unused?
						bit 3 set = Unknown use, can be set =1 and sent to GD-77 as such, but is read back as =0**
						bit 2 set = Unknown use, can be set =1 and sent to GD-77 as such, but is read back as =0  
						bit 1 set = Unused?
						NB: the CPS protects bit 3 from being set multiple ways; if this is bypassed, the firmware
						in the radio will force it back to being unset

FD	253		General settings:	bit 8 (MSB) = Unused?
						bit 7 set = Unused?
						bit 6 set = Unused?
						bit 5 set = Unused?
						bit 4 set = TX exit tone
						bit 3 set = Unused?
						bit 2 set = Unused?
						bit 1 set = Unused?

FE			Spare? filled with $00

FF			Spare? filled with $00

100-107	256-263		Programming password text.  WARNING: do not edit to contain non-standard characters!  You will
			need to factory default the radio by holding side button 1 + number 1 key while switching on.

108			Spare? filled with $01  Can't change?

109	265		Buttons: Long press duration in steps
10A	266		Buttons: SK1 short press assignment
10B	267		Buttons: SK1 long press assignment
10C	268		Buttons: SK2 short press assignment
10D	269		Buttons: SK2 long press assignment
10E	270		Buttons: TK short press assignment
10F	271		Buttons: TK long press assignment

110-	272-		Buttons: quick key assignments 1-6
127	295		

128			Unknown, $01 / $20

129-			Spare?  Filled with $00 (7 bytes) can't be changed?
12F

130			Unknown, filled with $07

131-			Spare?  Filled with $00 (31 bytes)
14F

150-			Spare?  Filled with $00 (32 bytes)
16F

170-	368-		Pre-defined text messages, 32 messages x 144 characters each
136F	4976

1370			Unknown, $01
1371			Unknown, $00
1372			Unknown, $07
1373			Unknown, $00
1374			Unknown, $00
1375			Unknown, $00
1376			Unknown, $00
1377			Unknown, $00

1378-	4984-		16 x 32 or 64 bit encryption key field
13F7	5111

13F8			Unknown, $01
13F9			Unknown, $0A
13FA			Unknown, $00
13FB			Unknown, $0A
13FC			Unknown, $00
13FD			Unknown, $00
13FE			Unknown, $00
13FF			Unknown, $00

1400-			DTMF general data settings
1476

1477-			Unknown, active data, largely 00 or FF
1587

1588-			Emergency system data
1787

1788-			Digital contact data (24 bytes per contact)
2F87

2F88-			DTMF contact data
3387

3388-			Unknown, filled with $FF (160 bytes)
3427

3428-			Unknown, active data to do with RX Group list?
3437

3438-			RX Group list data (48 bytes per RX Group list)
3737

3738-			Unknown, active data? (8 bytes)
373F

3740-			General Zone data?
378F

3790-			Channel data, channels 1-128 only
538F

5390-			Unknown, active data? (24 bytes)
53A7

53A8-			Scan list data
5627

5628-			Spare data?  Filled with $FF (7920 bytes)
7517

7518	29976		Boot:	Bit 8 (MSB) = Unused?
				bit 7 set = Unused?
				bit 6 set = Unused?
				bit 5 set = Unused?
				bit 4 set = Unused?
				bit 3 set = Unused?
				bit 2 set = Unused?
				bit 1 set = 1=Intro screen picture, 0=Char string

7519	29977		Boot:	Bit 8 (MSB) = Unused?
				bit 7 set = Unused?
				bit 6 set = Unused?
				bit 5 set = Unused?
				bit 4 set = Unused?
				bit 3 set = Unused?
				bit 2 set = Unused?
				bit 1 set = Power on password enable

751A			Unknown: $00

751B			Unknown: $00

751C-			Power on password
751E

751F			Unknown: $00

7520-	29984-		Data relating to Number key quick contact access
7536	30006

7537			Unknown: $00	

7538	30008		Menu: Menu hang time in steps

7539	30009		Menu:	Bit 8 (MSB) = Contact - Remote monitor
				bit 7 set = Contact - Radio check
				bit 6 set = Contact - Manual dial
				bit 5 set = Contact - Edit
				bit 4 set = Contact - call alert
				bit 3 set = Scan - edit list
				bit 2 set = Scan - scan
				bit 1 set = Basic - information

753A	30010		Menu:	Bit 8 (MSB) = Utilities - Intro screen
				bit 7 set = Utilities - Backlight
				bit 6 set = Utilities - Power
				bit 5 set = Utilities - Tones/alerts
				bit 4 set = Utilities - talkaround
				bit 3 set = Contact - One key dial
				bit 2 set = Contact - Radio disable
				bit 1 set = Contact - Radio enable

753B	30011		Menu:	Bit 8 (MSB) = Call Log - Answered 
				bit 7 set = Call Log - Missed
				bit 6 set = Utilities - Password & lock
				bit 5 set = Utilities - VOX
				bit 4 set = Utilities - Privacy
				bit 3 set = Utilities - Squelch
				bit 2 set = Utilities - LED indicator
				bit 1 set = Utilities - keypad lock

753C	30012		Menu:	Bit 8 (MSB) = Unused?
				bit 7 set = Unused? 
				bit 6 set = Unused?
				bit 5 set = Unused? 
				bit 4 set = Unused?
				bit 3 set = Utilities - Double standby
				bit 2 set = Utilities - Channel display
				bit 1 set = Call Log - Outgoing radio

753D	30013		Menu:	Bit 8 (MSB) = Unused? 
				bit 7 set = Unused? 
				bit 6 set = Unused? 
				bit 5 set = Unused? 
				bit 4 set = Unused?
				bit 3 set = Unused?
				bit 2 set = Unused?
				bit 1 set = Unused?

753E	30014		Menu:	Bit 8 (MSB) = Utilities - Channel display mode Frequency
				bit 7 set = Utilities - Channel display mode Name
							(bit 7 & 8 not set = channel number mode)
				bit 6 set = Unused? 
				bit 5 set = Unused?
				bit 4 set = Utilities - Backlight 0=always, 1=timed
				bit 3 set = Utilities - Backlight: if always, 0=on, 1=off.  If timed, 0=5sec, 1=10sec
				bit 2 set = Utilities - Keypad lock time
				bit 1 set = Utilities - Keypad lock time

753F	30015		Menu:	Bit 8 (MSB) = Utilities - Double standby - double single
				bit 7 set = Utilities - Double standby - double double
							(bit 7 & 8 not set = off)
				bit 6 set = Utilities - Key tone
				bit 5 set = Utilities - 1=Chinese menu, 0=English
				bit 4 set = Unused?
				bit 3 set = Unused?
				bit 2 set = Unused?
				bit 1 set = Unused?

7540-			Boot:	Line 1 text
754E

754F			Unknown: $FF

7550-			Boot:	Line 2 text
755E

755F-			Spare?  Filled with $FF (2721 bytes)
7FFF

8000-			Unknown, mostly $FF or $00, one $01
802F

8030-			Zone data
AF0F

AF10-			Spare?  Filled with $00 (65 bytes)
AF50

AF51-			Unknown, filled with alternating $00, $01 (32 bytes)
AF70

AF71-			Unknown, some active data
B1BF

B1C0-			Channel data, channels 129-1024
1761F

17620-			Spare, filled with $FF (35296 bytes)
1FFFF