GPIO — General purpose input/output

The general purpose input/output (GPIO) is organized as one port with up to 32 I/Os (dependent on package) enabling access and control of up to 32 pins through one port. Each GPIO can be accessed individually.

GPIO has the following user-configurable features:

Up to 32 GPIO
8 GPIO with Analog channels for SAADC, COMP or LPCOMP inputs
Configurable output drive strength
Internal pull-up and pull-down resistors
Wake-up from high or low level triggers on all pins
Trigger interrupt on state changes on any pin
All pins can be used by the PPI task/event system
One or more GPIO outputs can be controlled through PPI and GPIOTE channels
All pins can be individually mapped to interface blocks for layout flexibility
GPIO state changes captured on SENSE signal can be stored by LATCH register

The GPIO Port peripheral implements up to 32 pins, PIN0 through PIN31. Each of these pins can be individually configured in the PIN_CNF[n] registers (n=0..31).

The following parameters can be configured through these registers:

Direction
Drive strength
Enabling of pull-up and pull-down resistors
Pin sensing
Input buffer disconnect
Analog input (for selected pins)

The PIN_CNF registers are retained registers. See POWER — Power supply chapter for more information about retained registers.

Pin configuration

Pins can be individually configured, through the SENSE field in the PIN_CNF[n] register, to detect either a high level or a low level on their input.

When the correct level is detected on any such configured pin, the sense mechanism will set the DETECT signal high. Each pin has a separate DETECT signal, and the default behaviour, as defined by the DETECTMODE register, is that the DETECT signal from all pins in the GPIO Port are combined into a common DETECT signal that is routed throughout the system, which then can be utilized by other peripherals, see Figure 1. This mechanism is functional in both ON and OFF mode.

Figure 1. GPIO Port and the GPIO pin details

Figure 1 illustrates the GPIO port containing 32 individual pins, where PIN0 is illustrated in more detail as a reference. All the signals on the left side of the illustration are used by other peripherals in the system, and therefore, are not directly available to the CPU.

Make sure that a pin is in a level that cannot trigger the sense mechanism before enabling it. Detect will go high immediately if the sense condition configured in the PIN_CNF registers is met when the sense mechanism is enabled. This will trigger a PORT event if the DETECT signal was low before enabling the sense mechanism. See GPIOTE — GPIO tasks and events.

See the following peripherals for more information about how the DETECT signal is used:

POWER: uses the DETECT signal to exit from System OFF.
GPIOTE: uses the DETECT signal to generate the PORT event.

When a pin's PINx.DETECT signal goes high, a flag will be set in the LATCH register, e.g. when the PIN0.DETECT signal goes high, bit 0 in the LATCH register will be set to '1'.

The LATCH register will only be cleared if the CPU explicitly clears it by writing a '1' to the bit that shall be cleared, i.e. the LATCH register will not be affected by a PINx.DETECT signal being set low.

If the CPU performs a clear operation on a bit in the LATCH register when the associated PINx.DETECT signal is high, the bit in the LATCH register will not be cleared.

The LDETECT signal will be set high when one or more bits in the LATCH register are '1'. The LDETECT signal will be set low when all bits in the LATCH register are successfully cleared to '0'.

If one or more bits in the LATCH register are '1' after the CPU has performed a clear operation on the LATCH registers, a rising edge will be generated on the LDETECT signal, this is illustrated in Figure 2.

Important: The CPU can read the LATCH register at any time to check if a SENSE condition has been met on one or more of the the GPIO pins even if that condition is no longer met at the time the CPU queries the LATCH register. This mechanism will work even if the LDETECT signal is not used as the DETECT signal.

The LDETECT signal is by default not connected to the GPIO port's DETECT signal, but via the DETECTMODE register it is possible to change the behaviour of the GPIO port's DETECT signal from the default behaviour described above to instead be derived directly from the LDETECT signal, see Figure 1. Figure 2 illustrates the DETECT signals behaviour for these two alternatives.

Figure 2. DETECT signal behavior

The input buffer of a GPIO pin can be disconnected from the pin to enable power savings when the pin is not used as an input, see Figure 1. Inputs must be connected in order to get a valid input value in the IN register and for the sense mechanism to get access to the pin.

Other peripherals in the system can attach themselves to GPIO pins and override their output value and configuration, or read their analog or digital input value, see Figure 1.

Selected pins also support analog input signals, see ANAIN in Figure 1. The assignment of the analog pins can be found in Pin assignments.

Important: When a pin is configured as digital input, care has been taken in the nRF52832 design to minimize increased current consumption when the input voltage is between V_IL and V_IH. However, it is a good practice to ensure that the external circuitry does not drive that pin to levels between V_IL and V_IH for a long period of time.

GPIO located near the RADIO

Radio performance parameters, such as sensitivity, may be affected by high frequency digital I/O with large sink/source current close to the radio power supply and antenna pins.

Refer to Pin assignments for recommended usage guidelines to maximize radio performance in an application.

Registers

Table 1. Instances
Base address	Peripheral	Instance	Description	Configuration
0x50000000	GPIO	GPIO	General purpose input and output		Deprecated
0x50000000	GPIO	P0	General purpose input and output

Table 2. Register Overview
Register	Offset	Description
OUT	0x504	Write GPIO port
OUTSET	0x508	Set individual bits in GPIO port
OUTCLR	0x50C	Clear individual bits in GPIO port
IN	0x510	Read GPIO port
DIR	0x514	Direction of GPIO pins
DIRSET	0x518	DIR set register
DIRCLR	0x51C	DIR clear register
LATCH	0x520	Latch register indicating what GPIO pins that have met the criteria set in the PIN_CNF[n].SENSE registers
DETECTMODE	0x524	Select between default DETECT signal behaviour and LDETECT mode
PIN_CNF[0]	0x700	Configuration of GPIO pins
PIN_CNF[1]	0x704	Configuration of GPIO pins
PIN_CNF[2]	0x708	Configuration of GPIO pins
PIN_CNF[3]	0x70C	Configuration of GPIO pins
PIN_CNF[4]	0x710	Configuration of GPIO pins
PIN_CNF[5]	0x714	Configuration of GPIO pins
PIN_CNF[6]	0x718	Configuration of GPIO pins
PIN_CNF[7]	0x71C	Configuration of GPIO pins
PIN_CNF[8]	0x720	Configuration of GPIO pins
PIN_CNF[9]	0x724	Configuration of GPIO pins
PIN_CNF[10]	0x728	Configuration of GPIO pins
PIN_CNF[11]	0x72C	Configuration of GPIO pins
PIN_CNF[12]	0x730	Configuration of GPIO pins
PIN_CNF[13]	0x734	Configuration of GPIO pins
PIN_CNF[14]	0x738	Configuration of GPIO pins
PIN_CNF[15]	0x73C	Configuration of GPIO pins
PIN_CNF[16]	0x740	Configuration of GPIO pins
PIN_CNF[17]	0x744	Configuration of GPIO pins
PIN_CNF[18]	0x748	Configuration of GPIO pins
PIN_CNF[19]	0x74C	Configuration of GPIO pins
PIN_CNF[20]	0x750	Configuration of GPIO pins
PIN_CNF[21]	0x754	Configuration of GPIO pins
PIN_CNF[22]	0x758	Configuration of GPIO pins
PIN_CNF[23]	0x75C	Configuration of GPIO pins
PIN_CNF[24]	0x760	Configuration of GPIO pins
PIN_CNF[25]	0x764	Configuration of GPIO pins
PIN_CNF[26]	0x768	Configuration of GPIO pins
PIN_CNF[27]	0x76C	Configuration of GPIO pins
PIN_CNF[28]	0x770	Configuration of GPIO pins
PIN_CNF[29]	0x774	Configuration of GPIO pins
PIN_CNF[30]	0x778	Configuration of GPIO pins
PIN_CNF[31]	0x77C	Configuration of GPIO pins

OUT

Address offset: 0x504

Write GPIO port

Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Id				f	e	d	c	b	a	Z	Y	X	W	V	U	T	S	R	Q	P	O	N	M	L	K	J	I	H	G	F	E	D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Id	RW	Field	Value Id	Value								Description
A	RW	PIN0										Pin 0
			Low	0								Pin driver is low
			High	1								Pin driver is high
B	RW	PIN1										Pin 1
			Low	0								Pin driver is low
			High	1								Pin driver is high
C	RW	PIN2										Pin 2
			Low	0								Pin driver is low
			High	1								Pin driver is high
D	RW	PIN3										Pin 3
			Low	0								Pin driver is low
			High	1								Pin driver is high
E	RW	PIN4										Pin 4
			Low	0								Pin driver is low
			High	1								Pin driver is high
F	RW	PIN5										Pin 5
			Low	0								Pin driver is low
			High	1								Pin driver is high
G	RW	PIN6										Pin 6
			Low	0								Pin driver is low
			High	1								Pin driver is high
H	RW	PIN7										Pin 7
			Low	0								Pin driver is low
			High	1								Pin driver is high
I	RW	PIN8										Pin 8
			Low	0								Pin driver is low
			High	1								Pin driver is high
J	RW	PIN9										Pin 9
			Low	0								Pin driver is low
			High	1								Pin driver is high
K	RW	PIN10										Pin 10
			Low	0								Pin driver is low
			High	1								Pin driver is high
L	RW	PIN11										Pin 11
			Low	0								Pin driver is low
			High	1								Pin driver is high
M	RW	PIN12										Pin 12
			Low	0								Pin driver is low
			High	1								Pin driver is high
N	RW	PIN13										Pin 13
			Low	0								Pin driver is low
			High	1								Pin driver is high
O	RW	PIN14										Pin 14
			Low	0								Pin driver is low
			High	1								Pin driver is high
P	RW	PIN15										Pin 15
			Low	0								Pin driver is low
			High	1								Pin driver is high
Q	RW	PIN16										Pin 16
			Low	0								Pin driver is low
			High	1								Pin driver is high
R	RW	PIN17										Pin 17
			Low	0								Pin driver is low
			High	1								Pin driver is high
S	RW	PIN18										Pin 18
			Low	0								Pin driver is low
			High	1								Pin driver is high
T	RW	PIN19										Pin 19
			Low	0								Pin driver is low
			High	1								Pin driver is high
U	RW	PIN20										Pin 20
			Low	0								Pin driver is low
			High	1								Pin driver is high
V	RW	PIN21										Pin 21
			Low	0								Pin driver is low
			High	1								Pin driver is high
W	RW	PIN22										Pin 22
			Low	0								Pin driver is low
			High	1								Pin driver is high
X	RW	PIN23										Pin 23
			Low	0								Pin driver is low
			High	1								Pin driver is high
Y	RW	PIN24										Pin 24
			Low	0								Pin driver is low
			High	1								Pin driver is high
Z	RW	PIN25										Pin 25
			Low	0								Pin driver is low
			High	1								Pin driver is high
a	RW	PIN26										Pin 26
			Low	0								Pin driver is low
			High	1								Pin driver is high
b	RW	PIN27										Pin 27
			Low	0								Pin driver is low
			High	1								Pin driver is high
c	RW	PIN28										Pin 28
			Low	0								Pin driver is low
			High	1								Pin driver is high
d	RW	PIN29										Pin 29
			Low	0								Pin driver is low
			High	1								Pin driver is high
e	RW	PIN30										Pin 30
			Low	0								Pin driver is low
			High	1								Pin driver is high
f	RW	PIN31										Pin 31
			Low	0								Pin driver is low
			High	1								Pin driver is high

OUTSET

Address offset: 0x508

Set individual bits in GPIO port

Read: reads value of OUT register.

Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Id				f	e	d	c	b	a	Z	Y	X	W	V	U	T	S	R	Q	P	O	N	M	L	K	J	I	H	G	F	E	D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Id	RW	Field	Value Id	Value								Description
A	RW	PIN0										Pin 0
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
B	RW	PIN1										Pin 1
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
C	RW	PIN2										Pin 2
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
D	RW	PIN3										Pin 3
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
E	RW	PIN4										Pin 4
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
F	RW	PIN5										Pin 5
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
G	RW	PIN6										Pin 6
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
H	RW	PIN7										Pin 7
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
I	RW	PIN8										Pin 8
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
J	RW	PIN9										Pin 9
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
K	RW	PIN10										Pin 10
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
L	RW	PIN11										Pin 11
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
M	RW	PIN12										Pin 12
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
N	RW	PIN13										Pin 13
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
O	RW	PIN14										Pin 14
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
P	RW	PIN15										Pin 15
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
Q	RW	PIN16										Pin 16
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
R	RW	PIN17										Pin 17
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
S	RW	PIN18										Pin 18
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
T	RW	PIN19										Pin 19
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
U	RW	PIN20										Pin 20
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
V	RW	PIN21										Pin 21
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
W	RW	PIN22										Pin 22
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
X	RW	PIN23										Pin 23
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
Y	RW	PIN24										Pin 24
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
Z	RW	PIN25										Pin 25
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
a	RW	PIN26										Pin 26
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
b	RW	PIN27										Pin 27
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
c	RW	PIN28										Pin 28
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
d	RW	PIN29										Pin 29
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
e	RW	PIN30										Pin 30
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect
f	RW	PIN31										Pin 31
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Set	1								Write: writing a '1' sets the pin high; writing a '0' has no effect

OUTCLR

Address offset: 0x50C

Clear individual bits in GPIO port

Read: reads value of OUT register.

Bit number				31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Id				f	e	d	c	b	a	Z	Y	X	W	V	U	T	S	R	Q	P	O	N	M	L	K	J	I	H	G	F	E	D	C	B	A
Reset 0x00000000				0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Id	RW	Field	Value Id	Value								Description
A	RW	PIN0										Pin 0
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
B	RW	PIN1										Pin 1
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
C	RW	PIN2										Pin 2
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
D	RW	PIN3										Pin 3
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
E	RW	PIN4										Pin 4
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
F	RW	PIN5										Pin 5
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
G	RW	PIN6										Pin 6
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
H	RW	PIN7										Pin 7
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
I	RW	PIN8										Pin 8
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
J	RW	PIN9										Pin 9
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
K	RW	PIN10										Pin 10
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
L	RW	PIN11										Pin 11
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
M	RW	PIN12										Pin 12
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
N	RW	PIN13										Pin 13
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
O	RW	PIN14										Pin 14
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
P	RW	PIN15										Pin 15
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
Q	RW	PIN16										Pin 16
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
R	RW	PIN17										Pin 17
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
S	RW	PIN18										Pin 18
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
T	RW	PIN19										Pin 19
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
U	RW	PIN20										Pin 20
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
V	RW	PIN21										Pin 21
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
W	RW	PIN22										Pin 22
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
X	RW	PIN23										Pin 23
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
Y	RW	PIN24										Pin 24
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
Z	RW	PIN25										Pin 25
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
a	RW	PIN26										Pin 26
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
b	RW	PIN27										Pin 27
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
c	RW	PIN28										Pin 28
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
d	RW	PIN29										Pin 29
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high
			Clear	1								Write: writing a '1' sets the pin low; writing a '0' has no effect
e	RW	PIN30										Pin 30
			Low	0								Read: pin driver is low
			High	1								Read: pin driver is high