#### [?]

Group Name	R	W	7	6	5	4	3	2	1	0	Description	H	D
Issue 2 keyboard	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Enable Issue 2 keyboard	■	0
NextSound			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Enable Multiple PSGs*	■	0
Timex Video Port Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Enable read of Port FFh (Timex)**	■	0
DACs Control			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Enable DACs (A-B-C-D)	■	0
Internal Speaker Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable Internal Speaker	■	1
PSG Stereo Mode Control	■	■	[colour: pink]	[colour: pink]	0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Select ABC	■	0
			[colour: pink]	[colour: pink]	1	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Select ACB
Contention Control	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Disable RAM and Port Contention		0
128K Banking Unlock Control	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Unlock Port 7FFDh D5 (Unlocked = 1)		0

\* Currently selected PSG is frozen when disabled\ \*\* Enabling Timex Video Port read hides the floating bus on **FFh** #### NextREG 09 (09h) – Peripheral 4 Settings

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Scanline Strength	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	0	0	Scanlines off
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	0	1	Scanlines at 50%
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	1	0	Scanlines at 25%
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	1	1	Scanlines at 12.5%
HDMI audio output Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	HDMI audio mute	■	0
divMMC mapRAM bit Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Reset bit 6 port E3h (Read is always 0)
Sprite Lockstep Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable Sprite ID Lockstep		0
PSG 0 Mono Mode Control	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable Mono	■	0
PSG 1 Mono Mode Control	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable Mono	■	0
PSG 2 Mono Mode Control	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable Mono	■	0

In Sprite Lockstep, **NextREG 52 (34h)** and Port **12347 (303Bh)** are in Lockstep #### NextREG 10 (0Ah) – Peripheral 5 Settings

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Mouse resolution Control	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	0	0	Low DPI	■
			[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	0	1	Default
			[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	1	0	Medium DPI
			[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	1	1	High DPI
Reserved	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green] 0	[colour: pink]	[colour: pink]	Reserved, must be 0		0
Mouse button swap Control	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	•	[colour: dark green]	[colour: pink]	[colour: pink]	Reverses (swaps) L & R mouse buttons	■	0
divMMC Automap Control	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	•	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	Enables divMMC Automap	■	0
Reserved	■	■	[colour: pink]	[colour: pink]	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	Reserved, must be 0	■	0
Multiface Type	■	■	0	0	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	Multiface +3¹	♦	0
			0	1	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	Multiface 128 v87.2²
			1	0	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	Multiface 128 v87.12³
			1	1	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	Multiface 1⁴

¹ Enables port 3Fh, disables port BFh\ ² Enables port BFh, disables port 3Fh\ ³ Enables port 9Fh, disables port 1Fh\ ⁴ Enables port 9Fh, disables port 1Fh #### NextREG 11 (0Bh) – Joystick Port Mode Selection

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Parameter (Bit Bang)	■	■	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	•	Copied to pin 7 of the active connector¹		1
Parameter (Clock)			[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	Hold high when clock becomes high
			[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	Run²
Parameter (UART)			[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	Redirect ESP UART_0 to connector³
			[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	Redirect Pi UART_1 to connector³
Reserved	■	■	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	Reserved, must be 0		0
I/OMode Control	■	■	[colour: pink]	[colour: dark green]	0	0	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	Bit Bang		0
			[colour: pink]	[colour: dark green]	0	1	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	Clock
			[colour: pink]	[colour: dark green]	1	0	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	UART on left joystick port
			[colour: pink]	[colour: dark green]	1	1	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	UART on right joystick port
Reserved	■	■	[colour: pink]	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	Reserved, must be 0		0
Joystick Port Mode Selection	■	■	0	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	Joysticks Enabled		0
			1	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: pink]	I/O Mode Enabled

¹ The state of output pin 7 is stored internally in a register and is retained across changing modes and while I/O is disabled\ ² CTC Ch. 3 is currently used to drive pin 7 in clock mode. Frequency= *f*_CTC3 ÷2\ ³ Tx out on pin 7, Rx in from pin 9, CTS_n in from pin 6. CTS_n is only active if the selected UART is in hardware flow control mode\ \* While in I/O mode, keyboard joystick types (Sinclair, Cursor etc) produce no readings but the current state of pins can still be read via the Kempston ports. When leaving I/O mode, joystick operation resumes after approximately 64 scanlines have passed #### NextREG 14 (0Eh) – Core Version (Sub minor number)

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Sub Minor Number	■		•	•	•	•	•	•	•	•	Core Sub Minor Version Number

See **NextREG 01 (01h)** for Major and Minor Core Version #### NextREG 15 (0Fh) – Board ID

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Board Revision	■		[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	0	0	0	ZX Spectrum Next Issue 2¹
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	0	0	1	ZX Spectrum Next Issue 3¹
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	0	1	0	ZX Spectrum Next Issue 4²
Reserved	■		[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Reserved

¹ XC6SLX16-2FTG256, 128 Mbit W25Q128JV Flash, 24-bit SPI, 64K\*8 Core size\ ² XC7A15T-1CSG324, 256 Mbit MX25L25645G Flash, 32-bit SPI, 64K\*34 Core size #### [?]

Group Name	R	W	7	6	5	4	3	2	1	0	Description	H	[?]
NMI Button State Flag	■		[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	NMI Button Pressed		[?]
Drive Button State Flag	■		[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Drive Button Pressed		[?]
	■		[colour: dark green]	•	•	•	•	•	[colour: pink]	[colour: pink]	Core ID (0-31)
Reserved	■		[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Reserved, must be 0		[?]
Core ID		■	[colour: pink]	[colour: dark green]	[colour: dark green]	•	•	•	•	•	Core ID (0-31)	♦	[?]
Reserved		■	[colour: pink]	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Reserved, must be 0		[?]
Start Core		■	•	[colour: dark green]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Reboot FPGA using selected core		[?]

Core ID with **D0** through **D4** can be set in configuration mode only #### NextREG 17 (11h) – Video Timing

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
VGA Timing	■	■	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	0	0	Base VGA timing, clk28 = 28000000	♦	[?]
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	0	1	VGA setting 1, clk28 = 28571429
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	1	0	VGA setting 2, clk28 = 29464286
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	1	1	VGA setting 3, clk28 = 30000000
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	0	0	VGA setting 4, clk28 = 31000000
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	0	1	VGA setting 5, clk28 = 32000000
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	1	0	VGA setting 6, clk28 = 33000000
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	1	1	Digital, clk28 =27000000
Reserved	■	■	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	Reserved, must be 0		[?]

50 Hz / 60 Hz depends on **NextREG 05 (05h):D2**\ NextREG writable in configuration mode only #### NextREG 18 (12h) – Layer 2 Active RAM Bank

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
Layer 2 Active RAM Bank	■	■	[colour: dark green]	•	•	•	•	•	•	•	Starting 16K RAM Bank		[?]
Reserved	■	■	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Reserved, must be 0		[?]

Soft reset resets the default to **8**. NextZXOS changes that to **9** #### NextREG 19 (13h) – Layer 2 Shadow RAM Bank

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
Layer 2 Shadow RAM Bank	■	■	[colour: dark green]	•	•	•	•	•	•	•	Starting 16K RAM Bank		[?]
Reserved	■	■	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Reserved, must be 0		[?]

Soft reset resets the default to **11**. NextZXOS changes that to **12** #### NextREG 20 (14h) – Global Transparency Colour

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
Global Transparency Mask	■	■	•	•	•	•	•	•	•	•	8-bit colour value		[?]

Default value upon soft reset is **E3h** (227)\ This value is 8-bit; the transparency colour is compared against the MSB of the actual 9-bi[?] colour; as such, two colours (with either value of B₀) are made transparent\ This setting only applies to Layer 2, Layer 0 and Layer 1. Sprites use **NextREG 75 (4Bh)** and Layer 3 uses **NextREG 76 (4Ch)** for transparency except in text mode #### NextREG 21 (15h) – Sprite and Layer System Setup

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
Sprite Engine Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Enable Sprites		[?]
Sprite Extended Area Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Enable Sprites over border		[?]
Set Layer Priority	■	■	[colour: pink]	[colour: pink]	[colour: pink]	0	0	0	[colour: pink]	[colour: pink]	S L U		[?]
			[colour: pink]	[colour: pink]	[colour: pink]	0	0	1	[colour: pink]	[colour: pink]	L S U
			[colour: pink]	[colour: pink]	[colour: pink]	0	1	0	[colour: pink]	[colour: pink]	S U L
			[colour: pink]	[colour: pink]	[colour: pink]	0	1	1	[colour: pink]	[colour: pink]	L U S
			[colour: pink]	[colour: pink]	[colour: pink]	1	0	0	[colour: pink]	[colour: pink]	U S L
			[colour: pink]	[colour: pink]	[colour: pink]	1	0	1	[colour: pink]	[colour: pink]	U L S
			[colour: pink]	[colour: pink]	[colour: pink]	1	1	0	[colour: pink]	[colour: pink]	(U|T)S(T|U)(B+L) combined¹
			[colour: pink]	[colour: pink]	[colour: pink]	1	1	1	[colour: pink]	[colour: pink]	(U|T)S(T|U)(B+L) combined¹
Sprite Border Clipping	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable Sprite Clipping in over border mode		[?]
Sprite Priority	■	■	[colour: pink]	0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Sprite 127 on top		[?]
			[colour: pink]	1	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Sprite 0 on top
LoRes Control	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable LoRes		[?]

1 Colours Clamped to [0,7]\ ULA means all ULA modes: Layers 0 and all Layer 1 types. Value upon soft reset is **000** #### NextREG 22 (16h) – Layer 2 Horizontal Scroll Control LSB

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
X Offset LSB	■	■	•	•	•	•	•	•	•	•	8-bit value of X Offset LSB (0 – 511)		[?]

MSB is in **NextREG 113 (71h)** #### NextREG 23 (17h) – Layer 2 Vertical Scroll Control

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
Y Offset	■	■	•	•	•	•	•	•	•	•	8-bit value of Y Offset		[?]

#### NextREG 24 (18h) – Layer 2 Clip Window Definition

Group Name	R	W	Data Bits								Description	H	[?]
			7	6	5	4	3	2	1	0
Coordinate (Xbeg,Xend,Ybeg,Yend)	■	■	•	•	•	•	•	•	•	•	8-bit value of Xbeg,Xend,Ybeg,Yend coordinate¹		[?]

¹ 1^st Write **X**_beg position – \*Resets to **0**\ 2^nd Write **X**_end position – \*Resets to **255**\ 3^rd Write **Y**_beg position – \*Resets to **0**\ 4^rh Write **Y**_end position – \*Resets to **191**\ Reads do not advance the clip coordinate – Use **NR 28 (1Ch)** to find out the current clip coordinate or to set the clip coordinate to X_beg. The **X** coordinates are internally doubled fo[?] higher resolution modes. This means that X_end =159 covers the full **320** resolution.