lpc2361 NXP Semiconductors, lpc2361 Datasheet - Page 30

• Manufacturer Part Number: lpc2361
• Description: Single-chip 16-bit/32-bit Mcu; Up To 128 Kb ?ash With Isp/iap, Ethernet, Usb 2.0 Device/host/otg, Can, And 10-bit Adc/dac
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC2361_62_3
Product data sheet
7.24.1 Reset
7.24.2 Brownout detection
7.24.3 Code security (Code Read Protection - CRP)
7.24 System control
The VBAT pin supplies power only to the RTC and the battery RAM. These two functions
require a minimum of power to operate, which can be supplied by an external battery.
When the CPU and the rest of chip functions are stopped and power removed, the RTC
can supply an alarm output that may be used by external hardware to restore chip power
and resume operation.
Reset has four sources on the LPC2361/62: the RESET pin, the Watchdog reset,
power-on reset, and the BrownOut Detection (BOD) circuit. The RESET pin is a Schmitt
trigger input pin. Assertion of chip Reset by any source, once the operating voltage attains
a usable level, starts the Wake-up timer (see description in
timer”), causing reset to remain asserted until the external Reset is de-asserted, the
oscillator is running, a fixed number of clocks have passed, and the flash controller has
completed its initialization.
When the internal Reset is removed, the processor begins executing at address 0, which
is initially the Reset vector mapped from the Boot Block. At that point, all of the processor
and peripheral registers have been initialized to predetermined values.
The LPC2361/62 includes 2-stage monitoring of the voltage on the V
voltage falls below 2.95 V, the BOD asserts an interrupt signal to the Vectored Interrupt
Controller. This signal can be enabled for interrupt in the Interrupt Enable Register in the
VIC in order to cause a CPU interrupt; if not, software can monitor the signal by reading a
dedicated status register.
The second stage of low-voltage detection asserts Reset to inactivate the LPC2361/62
when the voltage on the V
the 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 LPC2361/62 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.
Rev. 03 — 11 November 2008
DD(3V3)
pins falls below 2.65 V. This Reset prevents alteration of
Single-chip 16-bit/32-bit MCU
Section 7.23.3 “Wake-up
LPC2361/62
DD(3V3)
© NXP B.V. 2008. All rights reserved.
pins. If this
30 of 50