SECURITY FEATURE
The following register describes the functionality to support security in the LPC47S42x.
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.
Device Disable Register
The Device Disable Register is located in the PME register block at offset 0x22 from the RUNTIME
REGISTERS BLOCK 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 control register for device disable register is defined in the “Runtime Registers” section.
SMBus CONTROLLER
Overview
The LPC47S42x supports SMBus. SMBus is a serial communication protocol between a computer host
and its peripheral devices. It provides a simple, uniform and inexpensive way to connect peripheral
devices to a single computer port. A single SMBus on a host can accommodate up to 125 peripheral
devices.
The SMBus protocol includes a physical layer based on the I
2
C
TM
serial bus developed by Philips, and
several software layers. The software layers include the base protocol, the device driver interface, and
several specific device protocols.
For a description of the SMBus protocol, please refer to the System Management Bus Specification
Revision 1.0, February 15, 1995, available from Intel Corporation.
The SMBus can assert both an nIO_PME and an nIO_SMI event when enabled and following an
SMBus interrupt. Refer to registers PME_STS6, PME_EN6, SMI_STS2 and SMI_EN2 in the Runtime
Registers section for more information.
The SMBus implementation in the LPC47S42x has the following additions over the I
2
C:
(1) Added Timeout Error (TE) Bit, in D6 of the SMBus Status Register.
(2) Added Timeout Interrupt Enable Bit D4 in the SMBus Control register.
151