Memory-mapped I/O ports

90000000 - General Purpose I/O (GPIO)

The GPIO registers are separated into 4 sections:

• Section 0: 90000000-9000003F
• Section 1: 90000040-9000007F
• Section 2: 90000080-900000BF
• Section 3: 900000C0-900000FF.

Each register is a word, and only bits 0-7 of each are used. There can be up to 32 devices accessed by this setup, each known as a GPIO. Each GPIO is defined by one of the 8 bits in one of the sections. The number of the GPIO is the section number times 8 plus the bit number. Each GPIO has a status bit and can cause interrupts.

The following addresses are offsets from the beginning of the GPIO section:

• +00 (R): Masked interrupt status ([+04] & [+08])
• +04 (R): Reads raw interrupt status (directly dependent on the GPIO status) or sticky interrupt status (becomes set when GPIO status changes) depending on bit in [+20]
• +04 (W): Write 1 to the bit to reset the sticky interrupt status.
• +08 (R): Reads current interrupt mask bit.
• +08 (W): Write 1 to the bit to enable interrupt (set mask bit to 1)
• +0C (W): Write 1 to the bit to disable interrupt (set mask bit to 0)

The following addresses should be changed with a read-modify-write pattern so as to not disturb other bits in the register.

• +10 (R/W): Setting bit to 0 will not allow GPIO status bit to change from its default (?)
• +14 (R/W): (?)
• +18 (R): Reads GPIO status bit.
• +1C (R/W): Setting bit to 1 will invert raw interrupt status (?)
• +20 (R/W): Setting bit to 1 will use sticky interrupt status in [+04], or setting to 0 will use raw interrupt status.
• +24 (R/W): (?)

Currently known GPIOs:

• GPIO 8 (Section 1, bit 0): Status bit is 0 if Reset Button is pressed.
• GPIO 24 (Section 3, bit 0): Status bit is 1 if a keypad is not plugged in. (TI-Nspire non-cas only?)

90010000 - Fast timer

The same interface as 900C0000/900D0000, but runs at the speed of the APB clock (22.5MHz) rather than 32kHz. See #900D0000 - Second timer Second timer for more info.

90020000 - Serial UART

Used to communicate with the RS232 serial port. The register interface is like that of 16550 UART used in PCs:

• 90020000 (R): Receiver Buffer Register
• 90020000 (W): Transmitter Holding Register
• 90020004 (R/W): Interrupt Enable Register
• 90020008 (R): Interrupt Identification Register
• 90020008 (W): FIFO Control Register
• 9002000C (R/W): Line Control Register
• 90020010 (R/W): Modem Control Register
• 90020014 (R): Line Status Register
• 90020018 (R): Modem Status Register
• 9002001C (R/W): Scratch Register

90060000 - Watchdog timer

Possibly an ARM SP805 or compatible.

90090000 - Real-Time Clock (RTC)

Might be an ARM PrimeCell PL031.

• 90090000 (R): Current time in seconds
• 90090004 (W): ?
• 90090008 (R/W): Sets the value of 90090000 (clock will not read new time until a couple seconds later). Reads last value written.
• 9009000C (W): ?
• 90090010 (W): ?
• 90090014 (R): ?

900A0000 - Miscellaneous

• 900A0000 (R): ?
• 900A0004 (R/W): Set bit 0x20 to enable TI-84+ keypad link port. Other bits likely control functions of peripherals as well.
• 900A0008 (W): Write a 2 to reset the CPU
• 900A0010 (R/W): Fast timer interrupt status/acknowledge (6-bit). Write "1" bits to reset the corresponding interrupt requests.
• 900A0014 (R/W): Fast timer interrupt mask (6-bit). Set bits to 1 if the corresponding bits in [900A0010] should trigger an IRQ.
• 900A0018 (R/W): Timer 1 interrupt status/acknowledge (6-bit). Write "1" bits to reset the corresponding interrupt requests.
• 900A001C (R/W): Timer 1 interrupt mask (6-bit). Set bits to 1 if the corresponding bits in [900A0018] should trigger an IRQ.
• 900A0020 (R/W): Timer 2 interrupt status/acknowledge (6-bit). Write "1" bits to reset the corresponding interrupt requests.
• 900A0024 (R/W): Timer 2 interrupt mask (6-bit). Set bits to 1 if the corresponding bits in [900A0020] should trigger an IRQ.
• 900A0028-900A002C (R): These registers together give a 64-bit number which comprises 56 data bits and 8 parity checking bits, allowing any single-bit error in it to be detected and corrected.
  • Parity bit 0: Check of all data bits
  • Parity bits 1, 2, 4, 8, 16, and 32: Checks of the data bits whose positions, expressed in binary, have that respective bit set.
  • Data bits 3, 5-7, 9-15, 17-31, and 33-55: Middle part of the calculator's Product ID
  • Data bits 56-57: Unknown
  • Data bits 58-62: "ASIC user flags"; must match the 80E0 field in an OS image. 01 = CAS, 00 = non-CAS.
  • Parity bit 63: Check of parity bits 1, 2, 4, 8, 16, and 32.

900B0000 - Power management

• 900B0000 (R/W): Clock speed load value
  • Bits 1-7: Multiply by 2 to get base/CPU ratio
  • Bit 8: If set, base clock is 27 MHz, else see bits 16-20
  • Bits 12-14: Add 1 to get CPU/AHB ratio
  • Bits 16-20: If bit 8 is clear, base clock is (300 - 6*this) MHz
• 900B0004 (W): ?
• 900B0008 (R/W): ?
• 900B000C (R/W): Clock speed control (write 4 to set the clock speed according to the value in 900B0000)
• 900B0010 (R/W): ON interrupt mask (1-bit). 1 if ON interrupt should be serviced or 0 if not.
• 900B0014 (R/W): Bit 0 is set if ON interrupt is requested. Bit 1 also causes an interrupt, but the cause is unknown (and it is not masked by [900B0010]). Write "1" bits to reset the requests.
• 900B0018 (R/W): ?
• 900B0020 (R/W): ?
• 900B0024 (R): Reads current clock speed value (see 900B0000 for details)
• 900B0028 (R): Bit 4 (0x10) clear when ON key pressed

900C0000 - First timer

Configured as ~488 Hz timer by the OS. Same port structure as #900D0000 - Second timer Second timer.

900D0000 - Second timer

Two timers are located here, but only the first can generate IRQs. IRQ status/mask is located at [900A0020]. Configured as a ~100 Hz timer by the OS.

• 900D0000 (R/W): Current IRQ timer value (16-bit). Set to 32 by the OS. Increases/decreases each [900D0004] ticks. The value written to this port is saved internally and can be reloaded automatically upon timer completion, depending on settings in [900D0008].
• 900D0004 (R/W): IRQ timer divider (16-bit). Ticks per count - 1. Set to 9 by the OS. Ticks are approximately 32 kHz.
• 900D0008 (R/W): IRQ timer control (5-bit).
  • Bit 4: Set to 1 to freeze timer.
  • Bit 3: Set to 1 for increasing timer, or to 0 for decreasing timer.
  • Bits 2-0: If 0, timer will count to zero and stop. If 1-6, timer will complete when it reaches the corresponding timer completion value and then reload with original timer value (see [900D0018] to [900D002C]). If 7, timer will never complete and runs infinitely.
• 900D000C (R/W): Current timer value (16-bit). Increases/decreases each [900D0010] ticks. The value written to this port is saved internally and can be reloaded automatically upon timer completion, depending on settings in [900D0014].
• 900D0010 (R/W): Timer divider (16-bit). Ticks per count - 1. Ticks are approximately 32 kHz.
• 900D0014 (R/W): Timer control (5-bit).
  • Bit 4: Set to 1 to freeze timer, or 0 to run timer.
  • Bit 3: Set to 1 for increasing timer, or to 0 for decreasing timer.
  • Bits 2-0: If 0, timer will count to zero and stop. If 1-6, timer will complete when it reaches the corresponding timer completion value (see [900D0018] to [900D002C]). If 7, timer will not complete and runs infinitely.
• 900D0018 (R/W): Timer completion value 1 (16-bit). If IRQ timer equals this value, bit 0 of the interrupt status becomes set.
• 900D001C (R/W): Timer completion value 2 (16-bit). If IRQ timer equals this value, bit 1 of the interrupt status becomes set.
• 900D0020 (R/W): Timer completion value 3 (16-bit). If IRQ timer equals this value, bit 2 of the interrupt status becomes set.
• 900D0024 (R/W): Timer completion value 4 (16-bit). If IRQ timer equals this value, bit 3 of the interrupt status becomes set.
• 900D0028 (R/W): Timer completion value 5 (16-bit). If IRQ timer equals this value, bit 4 of the interrupt status becomes set.
• 900D002C (R/W): Timer completion value 6 (16-bit). If IRQ timer equals this value, bit 5 of the interrupt status becomes set.
• 900D0030 (R/W): Unknown 6-bit value.

900E0000 - Keypad

• 900E0008 (R/W): Keypad interrupt status/acknowledge (2-bit). Bit 1 is set when a key is pressed or released, and bit 0 has an unknown cause.. Write "1" bits to acknowledge.
• 900E000C (R/W): Keypad interrupt mask (2-bit). Set each bit to 1 if the corresponding event in [900E0008] should cause an interrupt.
• 900E0010-900E001F (R, halfword): Keypad map (see below)
• 900E0044 (R/W): Unknown.

900E0010-900E001F - Keypad map

Each bit represents a key. If bit is cleared, the key is being pressed. Only bits 0 to 10 are used in each halfword. The mapping depends on the currently used keypad (TI-Nspire or TI-84+).

TI-Nspire keypad map:

offset	bit 0	bit 1	bit 2	bit 3	bit 4	bit 5	bit 6	bit 7	bit 8	bit 9	bit 10
0012	,	+	W	3	V	2	U	1	T	e^x	pi
0014	?	-	S	6	R	5	Q	4	P	10^x	EE
0016	:	*	O	9	N	8	M	7	L	x^2	i
0018	"	/	K	tan	J	cos	I	sin	H	^	>
001A	'	cat	G	)	F	(	E	var	D	caps	<
001C	flag	click	C	home	B	menu	A	esc		tab	---
001E	up	u+r	right	r+d	down	d+l	left	l+u	clear	ctrl	=

TI-84+ keypad map:

offset	bit 0	bit 1	bit 2	bit 3	bit 4	bit 5	bit 6	bit 7	bit 8	bit 9	bit 10
0010	down	left	right	up	---	---	---	---	---	---	---
0012	enter	+	-	*	/	^	clear	---	---	---	---
0014	(-)	3	6	9	)	tan	vars	---	---	---	---
0016	.	2	5	8	(	cos	prgm	stat	---	---	---
0018	0	1	4	7	,	sin	apps	X	---	---	---
001A	---	sto	ln	log	x^2	x^-1	math	alpha	---	---	---
001C	graph	trace	zoom	wind	y=	2nd	mode	del	---	---	---
001E	---	---	---	---	---	---	---	---	---	---	---

900F0000 - Unknown

• 900F0020 (R/W): LCD contrast. Valid values range from 0x6B to 0x95; normal value is 0x80

90100000 - TI-84 Plus link port

• 90100000 (W): Write to bits 0-1 to hold I/O link lines low or let them go high. 1=high, 0=low.
• 90100000 (R): Bits 0-1 hold the status of the I/O link lines. 1=high, 0=low. Bits 4-5 hold the last value outputted to bits 0-1.
• 90100004 (R/W): Unknown. The OS writes 0x80 here during initialization.
• 90100008 (R): Unknown. Bit 0x40 is set if any link lines are low.

90110000 - LED

• 90110B00 (R/W): Control register
  • Bit 0: Set this bit to enable green light blink data. If green blink data iteration is not on, the green light state is read from bit 0 of green blink data.
  • Bit 1: Set this bit and bit 6 to enable green blink data iteration.
  • Bit 2: Set this bit to force green light off. Overrides bit 4.
  • Bit 3: Set this bit to force red light off. Overrides bits 5 and 13.
  • Bit 4: Set this bit to force green light on.
  • Bit 5: Set this bit to force red light on.
  • Bit 6: See this bit and bit 1 to enable green blink data iteration. Reset before modifying green blink data or delay.
  • Bit 9: Set this bit to enable red light blink data. If red blink data iteration is not on, the red light state is read from bit 0 of red blink data.
  • Bit 10: Set this bit and bit 12 to enable red blink data iteration.
  • Bit 12: Set this bit and bit 10 to enable red blink data iteration. Reset before modifying red blink data or delay.
  • Bit 13: Forces red light on if bit 4 is 0, or red light off if bit 4 is 1. (?)
• 90110B04 (R/W): Green blink data. 32 bits of on and off state, represented by 1 and 0. Iteration is done from bit 31 to bit 0 repeatedly.
• 90110B08 (R/W): Green blink delay (negative). OS sets this to -2048.
• 90110B0C (R/W): Red blink data. 32 bits of on and off state, represented by 1 and 0. Iteration is done from bit 31 to bit 0 repeatedly.
• 90110B10 (R/W): Red blink delay (negative). OS sets this to -2048.

Note: If red and green lights are on at the same time, the color becomes yellow.

A4000100-A40096FF - Screen

Read-write, byte, half-word, word

Screen buffer. The upper left corner is the first byte. Each grayscaled pixel is 4-bit long. 1111 is white, 0000 is black.

AC000000 - SD Host Controller

See http://www.sdcard.org/developers/tech/host_controller/simple_spec/

B0000000 - USB OTG controller

Appears similar to the USB interface on Freescale Semiconductor's microcontrollers.

• Module identification registers
  • B0000000 (R): ID - Identification register
  • B0000004 (R): HWGENERAL - General hardware parameters
  • B0000008 (R): HWHOST - Host hardware parameters
  • B000000C (R): HWDEVICE - Device hardware parameters
  • B0000010 (R): HWTXBUF - TX buffer hardware parameters
  • B0000014 (R): HWRXBUF - RX buffer hardware parameters
• Capability registers
  • B0000100 (R): CAPLENGTH - Capability registers length
  • B0000102 (R): HCIVERSION - Host controller interface version
  • B0000104 (R): HCSPARAMS - Host controller structural parameters
  • B0000108 (R): HCCPARAMS - Host controller capability parameters
  • B0000120 (R): DCIVERSION - Device controller interface version
  • B0000124 (R): DCCPARAMS - Device controller capability parameters
• Operational registers
  • B0000140 (R/W): USBCMD - USB command
  • B0000144 (R/W): USBSTS - USB status
  • B0000148 (R/W): USBINTR - USB interrupt enable
  • B000014C (R/W): FRINDEX - USB frame index
  • B0000150 (R): CTRLDSSEGMENT - 4G segment selector (always 0?)
  • B0000154 (R/W): PERIODICLISTBASE - Frame list base address
  • B0000158 (R/W): ASYNCLISTADDR - Next asynchronous list address
  • B000015C (R/W): TTCTRL - TT status and control
  • B0000160 (R/W): BURSTSIZE - Programmable DMA burst size
  • B0000164 (R/W): TXFILLTUNING - Host TT Xmit pre-buffer packet tuning
  • B0000180 (R): CONFIGFLAG - Configured flag register (always 1?)
  • B0000184 (R/W): PORTSC - Port status and control
  • B00001A4 (R/W): OTGSC - On-The-Go status and control
  • B00001A8 (R/W): USBMODE - USB device mode
  • B00001AC (R/W): ENDPOINTSETUPSTAT - Endpoint setup status
  • B00001B0 (R/W): ENDPTPRIME - Endpoint initialization
  • B00001B4 (R/W): ENDPTFLUSH - Endpoint de-initialize
  • B00001B8 (R): ENDPTSTATUS - Endpoint status
  • B00001BC (R/W): ENDPTCOMPLETE - Endpoint complete
  • B00001C0 (R/W): ENDPTCTRL0 - Endpoint control 0
  • B00001C4 (R/W): ENDPTCTRL1 - Endpoint control 1
  • B00001C8 (R/W): ENDPTCTRL2 - Endpoint control 2
  • B00001CC (R/W): ENDPTCTRL3 - Endpoint control 3

C0000000 - LCD controller

Probably an ARM PrimeCell PL110 or something compatible.

• C0000010 (R/W): Frame Base Address. Holds the address to read pixel data from. Set to A4000100 by the OS.
• C0000018 (R/W): Interrupt mask.
• C000001C (R/W): LCD Control
  • Bit 0: LCD controller enable.
  • Bits 1-3: LCD bits per pixel.
    • 000 = 1 bpp
    • 001 = 2 bpp
    • 010 = 4 bpp (default setting of OS)
    • 011 = 8 bpp
    • 100 = 16 bpp (holds the literal 16-bit palette value instead of a palette index)
    • 101 = 24 bpp (not applicable to TI-Nspire's STN LCD)
    • 110,111 = reserved
  • Bit 4: Set to 1 if STN LCD is monochrome, or 0 if color. Should be set to 1 on TI-Nspire.
  • Bit 5: Set to 1 if LCD is TFT, or 0 if STN. Should be set to 0 on TI-Nspire.
  • Bit 6: Set to 1 if monochrome STN LCD has a 8-bit interface, or 0 if 4-bit. Should be set to 1 on TI-Nspire.
  • Bit 7: Set to 1 if LCD is dual panel STN, or 0 if single-panel. Should be set to 0 on TI-Nspire.
  • Bit 8: Set to 1 if the palettes are read as BGR, or 0 if RGB. Since monochrome displays use only the R color, it is possible to store a secondary palette in the B color and switch instantly by flipping this bit.
  • Bit 9: Set to 1 if the bytes in each word are to be read as big-endian, or 0 if little-endian. Set to 0 by the OS.
  • Bit 10: Set to 1 if the pixels within each byte are to be read as big-endian, or 0 if little-endian. Only affects 1,2,4 bpp modes. Set to 1 by the OS.
  • Bit 11: LCD power enable.
  • Bits 12-13: Vertical compare interrupt region.
    • 00 = start of vertical synchronization
    • 01 = start of back porch
    • 10 = start of active video
    • 11 = start of front porch
  • Bits 14-15: Reserved.
  • Bit 16: LCD DMA FIFO Watermark Level.
  • Bits 17-31: Reserved.
• C0000020 (R): Raw interrupt status.
  • Bit 1: FIFO Underflow
  • Bit 2: LCD next address base update. Signifies that a new Frame Base Address value can be loaded for double-buffering.
  • Bit 3: Vertical compare. Set when one of four vertical regions (specified by the LCD Control register) is reached.
  • Bit 4: AHB Master bus error.
• C0000024 (R): Masked interrupt status.
• C0000028 (W): Interrupt clear. Write a 1 to each bit to clear.
• C000002C (R): Address that is currently being read from (approximate)
• C00000200-C00003FF (R/W): 256 color palettes (each is a half-word).
  • Bits 0-4: Red palette data (bits 1-4 are the grayscale data on the Nspire screen)
  • Bits 5-9: Green palette data (unused on Nspire)
  • Bits 10-14: Blue palette data (bits 11-14 are the grayscale data on the Nspire screen if BGR mode is set)
  • Bit 15: Intensity (unused on Nspire)

CC000000 - SHA-256 hash generator

Implements the SHA-256 hash algorithm, which is used in cryptographic signatures.

• CC000000 (R): Busy if bit 0 set
• CC000000 (W): Write 0x10 and then 0x0 to initialize. Write 0xE to process first block, 0xA to process subsequent blocks
• CC000008 (R/W): ?
• CC000010-CC00004F (W): 512-bit block
• CC000060-CC00007F (R): 256-bit state

DC000000 - Interrupt controller

Registers that operate on sets of IRQs are bitmaps, with bit 0 corresponding to IRQ 0, and so on.

• DC000000 (R): Masked IRQ status (always equal to [DC000004] & [DC000008])
• DC000004 (R): Raw interrupt status or sticky interrupt status, depending on bitfield in DC000204
• DC000004 (W): Resets a set of sticky interrupts
• DC000008 (R): Current set of enabled IRQs
• DC000008 (W): Enable a set of IRQs
• DC00000C (R): Mirror of DC000008
• DC00000C (W): Disable a set of IRQs
• DC000020 (R): Reads current IRQ number (no side effects)
• DC000024 (R): Reads current IRQ number, copies the value in DC00002C to DC000028, writes the priority of the current IRQ to DC00002C
• DC000028 (R): Reading this register will reset the IRQ request. The value read is whatever was last copied by reading DC000024
• DC00002C (R/W): 4-bit value. IRQs with priority greater than or equal to this value will not be requested
• DC000100 (R): Masked FIQ status (always equal to [DC000104] & [DC0000108])
• DC000104 (R): Raw interrupt status or sticky interrupt status, depending on bitfield in DC000204
• DC000104 (W): Resets a set of sticky interrupts
• DC000108 (R): Current set of enabled FIQs
• DC000108 (W): Enable a set of FIQs
• DC00010C (R): Mirror of DC000108
• DC00010C (W): Disable a set of FIQs
• DC000120 (R): Reads current FIQ number (no side effects)
• DC000124 (R): Reads current FIQ number, copies the value in DC00012C to DC000128, writes the priority of the current IRQ to DC00012C
• DC000128 (R): Reading this register will reset the FIQ request. The value read is whatever was last copied by reading DC000124
• DC00012C (R/W): 4-bit value. FIQs with priority greater than or equal to this value will not be requested
• DC000200 (R/W): Bits that are 0 will invert the corresponding raw interrupt status bit. Typically this register should hold 0xFFFFFFFF.
• DC000204 (R/W): Bits that are 1 will cause the corresponding bit in DC000004 and DC000104 to read the sticky interrupt status. Bits that are 0 will cause the corresponding bit to read the raw interrupt status.
• DC000208 (R/W): ?
• DC000300-DC0003FF (W): IRQ priority (0-7). One register per IRQ. Lower values indicate higher priority.

Here is a list of known IRQ numbers:

• IRQ 1 = Serial UART
• IRQ 3 = Watchdog timer
• IRQ 7 = GPIO
• IRQ 8 = USB OTG
• IRQ 9 = USB HOST
• IRQ 11 = ADC
• IRQ 13 = SD Host Controller
• IRQ 14 = Unknown (?)
• IRQ 15 = Power management
• IRQ 16 = Keypad
• IRQ 17 = Fast timer
• IRQ 18 = First timer
• IRQ 19 = Second timer
• IRQ 21 = LCD controller
• IRQ 22 = TI-84 Plus link port (?)