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AN671
PRECISION32™ PORT I/O CROSSBAR DECODER
1. Introduction
Precision32™ devices use one or more Port I/O Crossbar Decoders to assign internal digital signals to Port I/O
pins. A crossbar decoder provides the system designer with flexibility to customize the pinout according to the
needs of the application. The Port I/O Crossbar Decoder is particularly useful in low pin count devices where the
number of internal digital signals outnumber the available I/O pins.
The crossbars are fully supported by the Silicon Labs Precision32 SDK, including Hardware Access Layer (HAL)
routines and code examples showing how to configure a crossbar for a particular peripheral. Additionally, the
Precision32 AppBuilder application provides a graphical interface to easily configure pins in a crossbar.
Figure 1 shows an example of how internal signals are routed to the Port Banks of SiM3U1xx devices through the
use of two crossbar decoders. Port Bank 0 (PB0) and Port Bank 1 (PB1) are connected to crossbar 0, and
Port Bank 2 (PB2) and Port Bank 3 (PB3) are connected to crossbar 1.
PB4.5 1
PB4.4 2
PB4.3 3
VSSHD 4
VIOHD 5
PB4.2 6
PB4.1 7
PB4.0 8
PB3.11 9
PB3.10 10
PB3.9 11
PB3.8 12
PB3.7 13
PB3.6 14
PB3.5 15
PB3.4 16
PB3.3 17
PB3.2 18
PB3.1 19
PB3.0 20
PB4
Independent of
the crossbars
Crossbar 0
(PB0 and PB1)
SiM3U167
80-Pin TQFP
Crossbar 1
(PB2 and PB3)
60 PB0.12
59 PB0.13
58 PB0.14
57 PB0.15
56 PB1.0
55 PB1.1
54 PB1.2/TRST
53 PB1.3/TDO/SWV
52 PB1.4/TDI
51 PB1.5/ETM0
50 PB1.6/ETM1
49 VIO
48 PB1.7/ETM2
47 PB1.8/ETM3
46 PB1.9/TRACECLK
45 SWCLK/TCK
44 SWDIO/TMS
43 PB1.10
42 PB1.11
41 PB1.12
Figure 1. Crossbar Example on a SiM3U167 Device
2. Relevant Documentation
Precision32 Application Notes are listed on the following website: www.silabs.com/32bit-mcu.
AN664: Precision32™ CMSIS and HAL User’s Guide
AN670: Getting Started with the Silicon Labs Precision32™ AppBuilder
Rev. 0.1 2/12
Copyright © 2012 by Silicon Laboratories
AN671