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Media Local Bus (MLB)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
27-39
Additionally, software may instruct the MLB to automatically disable a logical channel when MLB frame
synchronization is lost. To enable this feature, software must set CSCLR
n
[FSCD], which causes hardware
to automatically clear the Channel Enable bit (CECHR
n
[CE]) when synchronization is lost.
Frame synchronization is not supported for asynchronous, control, or isochronous channels.
27.4.9
Loop Back Test Mode
In order to facilitate silicon debug of the MLB Device, hardware supports the
Loop-Back Test Mode
. This
mode allows testing of the MLB pads, physical layer, link layer, channel protocol, and local channel buffer.
When the DCCR[LBM] bit is set, a data path is enabled which allows RX data from Channel 0 to be sent
out as TX data on Channel 1.
illustrates the
Loop-Back Test Mode
data path.
Figure 27-22. Loop-Back Test Mode Data Path
For
Loop-Back Test Mode
operation, software must perform the following steps:
•
Set the logical
ChannelAddresses
for Channel 0 and 1. (They cannot be the same address.)
•
Enable Channel 0 for receiving synchronous, asynchronous, control, or isochronous data.
•
Enable Channel 1 for transmitting the same channel data type as Channel 0.
•
Set the Loop-Back Mode bit (DCCR[LBM]).
Restrictions on the
Loop-Back Test Mode
are as follows:
•
No protocol errors or breaks are allowed on either the RX or TX channel.
•
Little-Endian mode must be disabled (DCCR[MLE] clear).
•
Isochronous packet lengths must be quadlet multiples.
•
Next Buffer Ready bits for Channels 0 and 1 must remain clear
(CSCR0[RDY] = CSCR1[RDY] = 0)
27.5
Initialization Information
The flowcharts in the following pages detail the intended software flow for the MLB Device peripheral.
These flowcharts are provided as examples only and are not intended as a source for firmware. Other valid
software flows are possible.
PADS
MediaLB Core
MediaLB
Link Logic
(Link Layer)
(Physical Layer)
MediaLB Interface
Channel 1
Local Buffer
1
Channel 0
Local Buffer
Channel 1
Protocol Engine
(TX)
Channel 0
Protocol Engine
(RX)
DCCR.LMB = 1
Summary of Contents for PXN2020
Page 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Page 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Page 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Page 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Page 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Page 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Page 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Page 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
Page 822: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 27 50 Freescale Semiconductor...
Page 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...