lpc2468fet208 NXP Semiconductors, lpc2468fet208 Datasheet - Page 44

• Manufacturer Part Number: lpc2468fet208
• Description: Lpc2468 Single-chip 16-bit/32-bit Micro; 512 Kb Flash, Ethernet, Can, Isp/iap, Usb 2.0 Device/host/otg, External Memory Interface
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2468_2
Preliminary data sheet
CAUTION
7.26.3 Code security (Code Read Protection - CRP)
7.26.4 AHB bus
The second stage of low-voltage detection asserts Reset to inactivate the LPC2468 when
the voltage on the V
flash as operation of the various elements of the chip would otherwise become unreliable
due to low voltage. The BOD circuit maintains this reset down below 1 V, at which point
the power-on reset circuitry maintains the overall Reset.
Both the 2.95 V and 2.65 V thresholds include some hysteresis. In normal operation, this
hysteresis allows the 2.95 V detection to reliably interrupt, or a regularly-executed event
loop to sense the condition.
This feature of the LPC2468 allows user to enable different levels of security in the system
so that access to the on-chip flash and use of the JTAG and ISP can be restricted. When
needed, CRP is invoked by programming a specific pattern into a dedicated flash location.
IAP commands are not affected by the CRP.
There are three levels of the Code Read Protection.
CRP1 disables access to chip via the JTAG and allows partial flash update (excluding
flash sector 0) using a limited set of the ISP commands. This mode is useful when CRP is
required and flash field updates are needed but all sectors can not be erased.
CRP2 disables access to chip via the JTAG and only allows full flash erase and update
using a reduced set of the ISP commands.
Running an application with level CRP3 selected fully disables any access to chip via the
JTAG pins and the ISP. This mode effectively disables ISP override using P2[10] pin, too. It
is up to the user’s application to provide (if needed) flash update mechanism using IAP
calls or call reinvoke ISP command to enable flash update via UART0.
The LPC2468 implements two AHB buses in order to allow the Ethernet block to operate
without interference caused by other system activity. The primary AHB, referred to as
AHB1, includes the Vectored Interrupt Controller, GPDMA controller, USB interface, and
16 kB SRAM.
The second AHB, referred to as AHB2, includes only the Ethernet block and an
associated 16 kB SRAM. In addition, a bus bridge is provided that allows the secondary
AHB to be a bus master on AHB1, allowing expansion of Ethernet buffer space into
off-chip memory or unused space in memory residing on AHB1.
In summary, bus masters with access to AHB1 are the ARM7 itself, the USB block, the
GPDMA function, and the Ethernet block (via the bus bridge from AHB2). Bus masters
with access to AHB2 are the ARM7 and the Ethernet block.
If level three Code Read Protection (CRP3) is selected, no future factory testing can be
performed on the device.
DD(3V3)
Rev. 02 — 16 October 2007
pins falls below 2.65 V. This Reset prevents alteration of the
Fast communication chip
LPC2468
© NXP B.V. 2007. All rights reserved.
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