UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 36 of 792
NXP Semiconductors UM10237
Chapter 3: LPC24XX System control
[1] The state of this bit is preserved through a software reset, and only a POR or a BOD event will reset it to its default value.
3.4 AHB Configuration
The AHB configuration register allows changing AHB scheduling and arbitration
strategies.

3.4.1 AHB Arbiter Configuration register 1 (AHBCFG1 - 0xE01F C188)

By default, the AHB1 access is scheduled round-robin (bit 0 = 1). For round-robin
scheduling, the default priority sequence will be CPU, DMA, AHB1, USB and LCD.
The AHB1 access priority can be configured as priority scheduling (bit 0 = 0) and priority
of the each of the AHB1 bus masters can be set by writing the priority value (highest
priority = 5, lowest priority = 1).
Masters with the same priority value are scheduled on a round-robin basis.
2 - - Reserved. User software should not write ones to reserved bits. The value
read from a reserved bit is not defined. NA NA
3 MCIPWR
Active
Level[1]
MCIPWR pin control. R/W 0
0 The MCIPWR pin is low.
1 The MCIPWR pin is high.
4 OSCRANGE Main oscillator range select. R/W 0
0 The frequency range of the main oscillator is 1 MHz to 20 MHz.
1 The frequency range of the main oscillator is 15 MHz to 24 MHz.
5 OSCEN Main oscillator enabl e. R/W 0
0 The main oscillator is disabled.
1 The main oscillator is enabled, and will start up if the correct external
circuitry is connected to the XTAL1 and XTAL2 pins.
6 OSCSTAT Main oscillator status. RO 0
0 The main oscillator is not ready to be used as a clock source.
1 The main oscillator is ready to be used as a clock source. The main
oscillator must be enabled via the OSCEN bit.
31:7 - - Reserved. User software should not write ones to reserved bits. The value
read from a reserved bit is not defined. -NA
Table 29. System Controls and Status register (SCS - address 0xE01F C1A0) bit description
Bit Symbol Value Description Access Reset
value
Table 30. AHB configuration register map
Name Description Access Reset value Address
AHBCFG1 Configures the AHB1 arbiter. R/W 0x0000 0145 0xE01F C188
AHBCFG2 Configures the AHB2 arbiter. R/W 0x0000 0145 0xE01F C18C