UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
16 of 362
NXP Semiconductors
UM10208
Chapter 4: LPC2800 Cache
The cache has 16 configurable pages, each being 2 megabytes in size. The cache treats
these 16 pages as if they occupy the bottom 32 Megabytes of the system memory map,
which is their default mapping. The cache can re-map any of these pages such that the
physical address is above the lower 32 megabytes.
, a diagram showing physical memory and a virtual page mapping is given.
On the left of the diagram, memory is shown with no remapping, as issued by the CPU.
On the right, a higher physical address is shown mapped into a lower address for caching
purposes. To accomplish this, a page is used as a virtual page. Accessing this virtual
page, the cache will re-map the AHB bus address to the higher address range during a
cache miss, cache flush or a write access to the virtual page.
Fig 4.
Cache operation
Word 0
Word 7
Word 8
Word 15
Read into
cache line 0
Way_0
4K bytes
Word 1
2M
bytes
128 * 8
Words
Read into
cache line 1
Second read
into cache line 0
Third read into
cache line 0
Way_1
4K bytes
128 * 8
Words
128 * 8
Words
line 0
line 128
line 1
line 0
line 128
line 1
Memory