NXP Semiconductors PXN2020, Reference Manual, Page: 775 / 1376

Media Local Bus (MLB)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 27-3
MLB device that it can transmit data for that logical channel during the next physical channel slot. One
quadlet later, the transmitting MLB device send out a MLB command byte on the signal information line
and the corresponding data on the data line. All other MLB devices (including the controller) have already
compared the logical channel address with their internal table of addresses to determine if they are the
intended recipient of the data on this logical channel.
The receiving MLB device responds with a receive status response on the signal information line one byte
after the transmitting device sends the MLB command byte. Note that synchronous data transmissions
(which is the only data format to support multiple receivers) are not acknowledged, but asynchronous,
control and isochronous data transmissions are acknowledged.
For more information about the Media Local Bus protocol, please refer to the Media Local Bus
Specification .
27.1.4 Modes of Operation
The byte order in which data is transferred between the MLB bus and the MLB device is always Big
Endian; however, a multiplexor at the local channel buffer allows software to select the data byte order of
data within system memory. Big Endian or Little Endian is selected via a software programmable
configuration bit DCCR[MLE].
Table 27-1 illustrates the Big Endian data format. Table 27-2 illustrates the Little Endian data format.
27.2 External Signal Description
The MLB peripheral contains three external pins to interface to the MLB controller. They are shown in
Table 27-3 .
Table 27-1. Big Endian Byte Order
Address data[31:24] data[23:16] data[15:8] data[7:0]
0x0000_0000 Byte 00 Byte 01 Byte 02 Byte 03
0x0000_0004 Byte 04 Byte 05 Byte 06 Byte 07
0x0000_0008 Byte 08 Byte 09 Byte 10 Byte 11
0x0000_000C Byte 12 Byte 13 Byte 14 Byte 15
Table 27-2. Little Endian Byte Order
Address data[31:24] data[23:16] data[15:8] data[7:0]
0x0000_0000 Byte 03 Byte 02 Byte 01 Byte 00
0x0000_0004 Byte 07 Byte 06 Byte 05 Byte 04
0x0000_0008 Byte 11 Byte 10 Byte 09 Byte 08
0x0000_000C Byte 15 Byte 14 Byte 13 Byte 12