PXD20RM Datasheet, PDF (869/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

22.4.4 Address Filter
Since the type of access (which internal client) is not tagged by the GFX2D master port, an address filter
is used to screen for addresses that are within four programmable address windows. Transactions with
detected addresses are modified according to the configuration parameters of the respective window.
Transactions with addresses that are outside all of the windows proceed without modifications.
If address regions overlap, window 0 has priority over window 1, which has priority over window 2, which
has priority over window 3. A window is disabled if LAST address is programmed to be less than or equal
to FIRST address.
22.4.5 Byte Swapper
The address filter is used to screen for transactions that need byte swapping. The purpose of the byte
swapper is to provide endianness compatibility across platforms. Transactions with detected addresses are
modified with the byte swapping parameters of the respective window. Transactions with addresses that
are outside all of the windows proceed without modifications.
The byte swapper is onlyThe byte swapper contains three cascaded multiplexers for the read data bus and
three cascaded multiplexers for the write data bus and byte strobes. The three type of multiplexers are:
1. Byte-wide swapper. See Figure 22-7.
2. Halfword-wide swapper. See Figure 22-8.
3. Word-wide swapper. See Figure 22-9.
DATA[63:0]
WSTRB[7:0]
bit
bit
63
32 31
0
00 11 22 33 44 55 66 77
WSTRB[7]
WSTRB[0]
76543210
11 00 33 22 55 44 77 66
63
32 31
0
bit
bit
67452301
WSTRB[7]
WSTRB[0]
DATA[63:0]
WSTRB[7:0]
Figure 22-7. Byte-wide Swap
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
22-9