#### [?]

Group Name	R	W	7	6	5	4	3	2	1	0	Description	H	D
AFTER SOFT RESET (Copied into bits D4 through D7)
ROM 0 (128K) Lock Enable	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	ROM 0 Lock Enable*	■	0
ROM 1 (48K) Lock Enablen	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	ROM 1 Lock Enable*	■	0
ALT ROM Availability Switch	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	ALT ROM visible ONLY during writes	■	0
ALT ROM Enable	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	ALT ROM Enable	■	0
IMMEDIATE
ROM 0 (128K) Lock Enable	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	ROM 0 Lock Enable*	■	0
ROM 1 (48K) Lock Enable	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	ROM 1 Lock Enable*	■	0
ALT ROM Availability Switch	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	ALT ROM visible ONLY during writes	■	0
ALT ROM Enable	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	ALT ROM Enable	■	0

\* The locking mechanism applies also if the alternative ROM is not enabled. For the +3/+3e and Next personalities if the two lock bits are **not 0**, then the corresponding ROM page is locked in place. Other personalities (models) use the bits to preferentially lock the corresponding 48K or 128K ROM in place #### NextREG 142 (8Eh) – ZX Spectrum 128K Memory Mapping

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
RAM bank 0-15	■	■	[colour: pink]	•	•	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Port 7FFDh D2:D0
			•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Port DFFDh D0
RAM bank in ports 7FFDh, DFFDh paging mode	■		[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	1	[colour: pink]	[colour: pink]	[colour: pink]	Returns 1		1
		■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	0	[colour: pink]	[colour: pink]	[colour: pink]	No change in RAM bank / MMU 6 / MMU 7
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	1	[colour: pink]	[colour: pink]	[colour: pink]	Change RAM bank
Normal Paging Mode		■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	0	[colour: pink]	[colour: pink]	Port 1FFDh D0
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Port 7FFDh D4
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Port 1FFDh D2
allRAM Paging Mode		■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	1	[colour: pink]	[colour: pink]	Port 1FFDh D0
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Port 1FFDh D1
			[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Port 1FFDh D2

Writes can affect all ports 7FFDh, DFFDh, 1FFDh\ Writes always change the ROM / allRAM mapping\ Writes immediately change the current MMU mapping as if by Port Write #### NextREG 143 (8Fh) – Memory Mapping Mode Control

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Memory Mapping Mode*	■	■	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	0	Standard ZX 128K / +3¹	■	0
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	0	1	Reserved
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	0	Pentagon 512K²
			[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	[colour: dark green]	1	1	Pentagon 1024K³
Reserved	■	■	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	[colour: pink]	Reserved, must be 0

1 Principally ports 7FFDh, DFFDh and 1FFDh\ 2 Principally port 7FFDh\ 3 768 Kb on unexpanded Next machines. Principally ports 7FFDh and EFF7h\ \* The mapping modes affect how ports 7FFDh, DFFDh, 1FFDh and EFF7h carry out memory paging #### NextREG 144 (90h) – PI GPIO Pin Output Enable 1/4

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 0	■		[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Pin 0 cannot be enabled		0
Pin 1	■		[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Pin 1 cannot be enabled		0
Pin 2	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Enable		0
Pin 3	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 4	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 5	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 6	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 7	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0

#### NextREG 145 (91h) – PI GPIO Pin Output Enable 2/4

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 8	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Enable		0
Pin 9	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Enable		0
Pin 10	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Enable		0
Pin 11	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 12	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 13	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 14	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 15	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0

#### NextREG 146 (92h) – PI GPIO Pin Output Enable 3/4

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 16	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Enable		0
Pin 17	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Enable		0
Pin 18	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Enable		0
Pin 19	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 20	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 21	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 22	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0
Pin 23	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0

#### NextREG 147 (93h) – PI GPIO Pin Output Enable 4/4 (MSB)

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 24	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Enable		0
Pin 25	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Enable		0
Pin 26	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Enable		0
Pin 27	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Enable		0

#### [?]

Group Name	R	W	7	6	5	4	3	2	1	0	Description	H	D
Pin 0	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Data		1
Pin 1	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Data		1
Pin 2	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Data		1
Pin 3	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Data		1
Pin 4	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		1
Pin 5	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		1
Pin 6	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		1
Pin 7	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		1

#### NextREG 153 (99h) – PI GPIO Pin State 2/4

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 8	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Data		1
Pin 9	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Data		0
Pin 10	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Data		0
Pin 11	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 12	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 13	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 14	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 15	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0

#### NextREG 154 (9Ah) – PI GPIO Pin State 3/4

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 16	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Data		0
Pin 17	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Data		0
Pin 18	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Data		0
Pin 19	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 20	■	■	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 21	■	■	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 22	■	■	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0
Pin 23	■	■	•	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	Data		0

#### NextREG 155 (9Bh) – PI GPIO Pin State 4/4 (MSB)

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Pin 24	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Data		0
Pin 25	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	Data		0
Pin 26	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Data		0
Pin 27	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	[colour: pink]	Data		0

Writes to the above registers only propagate to the **PI GPIO** when the corresponding pin has its output enabled by **NextREG 144 (90h)** to **147 (93h)** #### NextREG 160 (A0h) – PI Peripheral Enable

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Enable SPI	■	■	[colour: dark green]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	•	Enable SPI on GPIO 7,8,9,10,11 *		0
Reserved	■	■	[colour: dark green]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	Reserved, must be 0
Enable I2C	■	■	[colour: dark green]	[colour: dark green]	[colour: pink]	[colour: pink]	•	[colour: dark green]	[colour: dark green]	[colour: pink]	Enable I2C on GPIO 2,3 *		0
PI Communication Type	■	■	[colour: dark green]	[colour: dark green]	[colour: pink]	0	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: pink]	Connect Rx to GPIO 15, Tx to GPIO 14¹,*		0
			[colour: dark green]	[colour: dark green]	[colour: pink]	1	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: pink]	Connect Rx to GPIO 14, Tx to GPIO 15 ²,*
Enable UART³	■	■	[colour: dark green]	[colour: dark green]	•	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: pink]	Enable UART on GPIO 14,15 *		0
Reserved	■	■	[colour: dark green] 0	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: dark green]	[colour: pink]	Reserved, must be 0

\* Overrides GPIO Enables\ **1** For communication with Pi HATS\ **2** For communication with Pi\ **3** GPIO 16, 17 will act as RTR_n and CTS_n if the UART is in Hardware Flow Control Mode #### NextREG 162 (A2h) – PI I²S Audio Control

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
Redirect to EAR	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	•	Direct I²S audio to EAR on port 0xFE		0
Reserved	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green] 1	[colour: pink]	Reserved, must be 1		1
Mute R control	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	[colour: pink]	•	[colour: dark green]	[colour: pink]	Mute right side		0
Mute L control	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	•	[colour: pink]	[colour: dark green]	[colour: pink]	Mute left side		0
Audio flow direction	■	■	[colour: pink]	[colour: pink]	[colour: dark green]	0	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	PCM_DOUT to Pi, PCM_DIN from Pi (Hats)		0
			[colour: pink]	[colour: pink]	[colour: dark green]	1	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	PCM_DOUT from Pi, PCM_DIN to Pi (pi)
Reserved	■		[colour: pink]	[colour: pink]	[colour: dark green] 0	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	Reserved, must be 0
I²S state	■	■	0	0	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	I²S Disabled		*
			0	1	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	I²S is mono, source R
			1	0	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	I²S is mono, source L
			1	1	[colour: dark green]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: dark green]	[colour: pink]	I²S is stereo

\* Soft reset sets a default of **00** #### NextREG 168 (A8h) – ESP WiFi GPIO Output Control

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
GPIO 0 Output Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	GPIO 0 Output Enable		0
GPIO 2 Output Control	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	0	[colour: pink]	[colour: pink]	GPIO 2 Output Enable¹		0

1 Fixed at 0; GPIO 2 is Read-Only #### NextREG 169 (A9h) – ESP WiFi GPIO Control

Group Name	R	W	Data Bits								Description	H	D
			7	6	5	4	3	2	1	0
GPIO 0	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	Read / Write GPIO 0		1
GPIO 2	■	■	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	[colour: pink]	•	[colour: pink]	[colour: pink]	Read / Write GPIO 2		1