UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 37 of 792
NXP Semiconductors UM10237
Chapter 3: LPC24XX System control
[1] Allowed values for nnn are: 101 (highest priority), 100, 011, 010, 001 (lowest priority).

3.4.1.1 Examples of AHB1 settings

The following examples use the LPC2478 to illustrate how to select the priority of each

AHB1 master based on different system requirements.

Table 31. AHB Arbiter Configuration register 1 (AHBCFG1 - address 0xE01F C188) bit
description
Bit Symbol Value Description Reset
value
0 sch eduler 0 Priority scheduling. 1
1 Uniform (round-robin) scheduling.
2:1 break_burst 00 Break all defined length bursts (the CPU does not create
defined bursts). 10
01 Break all defined length bursts greater than four-beat.
10 Break all defined length bursts greater than eight-beat.
11 Never break defined length bursts.
3 quantu m_type 0 A quantum is an AHB clock. 0
1 A quantum is an AHB bus cycle.
7:4 quantum_size Controls the type of arbitration and the number of quanta
before re-arbiration occurs. 0100
0000 Preemptive, re-arbitrate after 1 AHB quantum.
0001 Preemptive, re-arbitrate after 2 AHB quanta.
0010 Preemptive, re-arbitrate after 4 AHB quanta.
0011 Preemptive, re-arbitrate after 8 AHB quanta.
0100 Preemptive, re-arbitrate after 16 AHB quanta.
0101 Preemptive, re-arbitrate after 32 AHB quanta.
0110 Preemptive, re-arbitrate after 64 AHB quanta.
0111 Preemptive, re-arbitrate after 128 AHB quanta.
1000 Preemptive, re-arbitrate after 256 AHB quanta.
1001 Preemptive, re-arbitrate after 512 AHB quanta.
1010 Preemptive, re-arbitrate after 1024 AHB quanta.
1011 Preemptive, re-arbitrate after 2048 AHB quanta.
1100 Preemptive, re-arbitrate after 4096 AHB quanta.
1101 Preemptive, re-arbitrate after 8192 AHB quanta.
1110 Preemptive, re-arbitrate after 16384 AHB quanta.
1111 Non- preemptive, infinite AHB quanta.
10:8 default_master nnn[1] Master 1 (CPU) is the default master. 001
14:12 EP1 nnn[1] External priori ty for master 1 (CPU) 000
19:16 EP2 nnn[1] External priori ty for master 2 (GPDMA) 000
22:20 EP3 nnn[1] External priori ty for master 3 (AHB1) 000
26:24 EP4 nnn[1] External priori ty for master 4 (USB) 000
30:28 EP5 nnn[1] External priori ty for master 5 (LCD) 000