TMC2005-JT SMSC Corporation, TMC2005-JT Datasheet - Page 11

• Manufacturer Part Number: TMC2005-JT
• Description: ARCNET 5 Port HUB Controller
• Manufacturer: SMSC Corporation

- Dead band at Normal mode (nMBx=1)
Option Feature for Jitter Filtering
When any RX ports receive the bigger jitter than its allowance, the TMC2005 may fail to receive the data
correctly and the network may be down.. However the below method to escape is effective for the case that a
momentary big jitter occurs under a special condition like an optical transceiver.
1)
The reference phase of the internal DPLL is changed from the first pulse to the second pulse by setting “0” to the big
jitter mode pins (nBJX). This setup is effective for the case that a big jitter occurs when rising up from DC state as
same as when using an optical transceiver with ATC function (refer to complement).
Note:
limits the maximum cable length and maximum node number.
[Complement] The big jitter may occur in the case of using an optical transceiver, especially an optical receiver that
has an ATC circuit that controls threshold level in proportion to received light strength. The first pulse especially after
long time idle has the big jitter but the second pulse is stabilized.
2)
In order to filter the jitter of edge in one side, it is effective to set reverse to pin SA, SB, SE to change the polarity of
RX port.
Note:
original 2.5Mbps, and the delay time affects the maximum cable length and maximum node number.
Option Feature for Noise Cut mode
The Noise cut mode is enabled by setting pin nMBx sets 0. The noise cut mode is a function to remove the ringing
noise and the reflection noise generated on the leading edge side of the input pulse to receive data input RXINx. The
position and the width of the “dead band” are shown in the figure below.
SMSC TMC2005-JT
Ideal waveform
(Active High)
Big jitter (BJ) mode
Changing polar of RX port
RXIN
The delay time of the TMC2005 becomes 400nS (at 2.5Mbps) longer than the normal mode. The delay time
Changing the polarity of RX port makes the delay time of the TMC2005 circuit a half bit (200nS) longer than
RXIN edge reference position:
Generated by adjacent phase of SYNC character (1,1,0)
dead band
Tdr/8 = 1 clock
Period of data rate (Tdr)
DATASHEET
Page 11
- Dead band at Noise cut mode (nMBx=0)
Ideal waveform
(Active High)
RXIN
RXIN edge reference position:
Generated by adjacent phase of SYNC character (1,1,0)
dead band: Noise cut band
Tdr/8 = 1 clock
Period of data rate (Tdr)
ARCNET 5 Port HUB Controller
Revision 1.0 (01-30-06)
Datasheet