
SMSC DS – LPC47M14X 
Page 122 
Rev. 03/19/2001 
6.18 SECURITY FEATURE 
The following register describes the functionality to support security in the LPC47M14x.  
6.18.1 
GPIO Device Disable Register Control 
The GPIO pin GP43 is used for the Device Disable Register Control (DDRC) function. Setting bits[3:2] of the GP43 
configuration register to ‘01’, selects the DDRC function for the GP43 pin.  When bits[3:2]=01 the GP43 pin is an 
input, with non-inverted polarity.  Bits[3:2] cannot be cleared by writing to these bits; they are cleared by VTR POR, 
VCC POR and Hard Reset.  That is, when the DDRC function is selected for this pin, it cannot be changed, except by a 
VCC POR, hard reset or VTR POR. 
When the DDRC function is selected for GP43, the Device Disable register is controlled by the value of the GP43 pin 
as follows: 
 
If the GP43 pin is high, the Device Disable Register is Read-Only. 
 
If the GP43 pin is low, the Device Disable Register is Read/Write. 
6.18.2 
The Device Disable Register is located in the PME register block at offset 0x22 from the PME_BLK base I/O address 
in logical device A.  Writes to this register are blocked when the GP43 pin is configured for the Device Disable 
Register Control function (GP43 configuration register bit 2 =1) and the GP43 pin is high. 
The configuration register for the device disable register is defined in the “Runtime Registers” section. 
Device Disable Register 
6.19 GAME PORT LOGIC 
The LPC47M14x implements logic to support a dual game port.  This logic includes the following for each game port: 
two 555 timers, two game port RC constant inputs (x-axis and y-axis), two game port button inputs and game port 
interface logic. The implementation of the Game Port uses a simple A/D converter constructed from a 555 timer to 
digitize the analog value of a potentiometer for the x-axis and y-axis of the joystick. 
The figure below illustrates the implementation of the game port logic in the LPC47M14x. 
Game software will write a byte to the game port to reset it, and then poll (read) the port until the x and y-axis RC time 
constant pins (TIMA,B) time out (return to zero).  The elapsed time indicates the resistance value of the potentiometer 
and in turn, the position of the joystick. 
JOYR
Joystick 1 Button 1
Joystick 1 Button 2
556
OUT1A
OUT1B
TRIG1A
TRIG1B
X-Axis
Y-Axis
TIM1A
TIM1B
JOYW
Vcc = 5V
Internal To LPC47M14x
Joystick 1
D0
D1
D2
D3
D4
D5
D6
D7
556
OUT2A
OUT2B
TRIG2A
TRIG2B
X-Axis
Y-Axis
TIM2A
TIM2B
Vcc = 5V
Joystick 2
Joystick 2 Button 1
Joystick 2 Button 2
J1B1
J1B2
J2B1
J2B2
J1X
J1Y
J2X
J2Y
Game Port
Register
Vcc = 5V
Vcc = 5V
Vcc = 5V
Internal To Joysticks