Broadcom BCM5221 User Manual

Product Application Note ■ BCM5221
7/7/00 ■ BCM5220
Broadcom Corporation
5221/5220-AN01 Product Application Note, Revision R Page 12
CABLE LENGTH MONITORING CAPABILITY
The DSP nature of the 10/100 receiver within the BCM5221 allows real-time access to equalizer states that provide cable
length estimate information.
Specifically, bits [14:12] in Shadow Register 1Bh provide a +/- 10 meter length estimate of the CAT 5 cable connected to the
receiver inputs of the 5221 (assuming of course that the far end station is operational). This estimate is accessed by simply
reading the aforementioned bits. This provides the user with an easily accessed and powerful diagnostic tool for determining
potential problems within the cable plant and/or associated connectors. See Table 1 for decode.
JTAG CONSIDERATIONS
The BCM5221 device incorporates JTAG as a shared function with several device input control and output LED functions.
This pin sharing should be carefully considered if the use of JTAG is required. This pin sharing approach provides JTAG
functionality within the feature-rich BCM5221.
JTAG test mode is only enabled when the active high JTAG_EN input is pulled high. When JTAG_EN is enabled, the follow-
ing pins become the JTAG test interface for the BCM5221.
Table 1: Cable Length Estimate
Register 1Bh
14, 13, 12
Cable Length in Meters
000 <20
001 20 to <40
010 40 to <60
011 60 to <80
100 80 to <100
010 100 to <120
100 120 to <140
010 >140
Table 2: JTAG Signals
JTAG Signal Type
BCM5221
KPB
BCM5221
KPT
Description
JTAG_EN I
PD
A2 64 JTAG Enable. Active high. When this signal is high, causes
the BCM5221 to enter JTAG test mode which enables
TRST#, TCK, TMS, TDI and TDO signals. For normal opera-
tion leave this pin unconnected.
TRST# I
PU
F7 38 Test Reset. This pin becomes JTAG TRST#. This is an asyn-
chronous active low reset input to JTAG TAP controller. This
signal is multiplexed with ANEN signal input.
TCK I
PU
F6 37 JTAG test clock input. This signal is multiplexed with F100
signal.
TMS I/O
PU
G8 36 Test Mode Select input. This signal is multiplexed with
SPD_LED# and ADV_PAUSE#.

Broadcom BCM5221 Specifications

General

Brand	Broadcom
Model	BCM5221
Category	Transceiver
Language	English