TMC2072-MT SMSC, TMC2072-MT Datasheet - Page 58

• Manufacturer Part Number: TMC2072-MT
• Description: IC CTRLR CIRC 100-TQFP DUAL MODE
• Manufacturer: SMSC
• Series: CircLink™r

Specifications of TMC2072-MT

• Controller Type: I/O Controller
• Interface: Transceiver
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 40mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 100-TQFP, 100-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 638-1023

2.13.2 Timer Expansion in Multi-Stage Cascade Connection
NOTE:
Revision 0.1 (06-07-07)
R e s p o n s e T im e r
An extra delay of 0.5 μs is added to the message when HUB is set to ON. A delay of 2.0 μs is also added
in the CMI coding/decoding processing when CMI is set to ON. When configuring a cascade connection
and setting both HUB and CMI to ON, a 2.5 μs (2.0 μs + 0.5 μs) delay is added to a message every time
the message passes a node.
This delay may make the response timer timeout in the CircLink, causing communication failure. The
response timer monitors responses from the nodes and is normally set to 74.6 μs. The one way
propagation delay time permitted for cable, HUB circuit, and CMI decoding/coding circuit is 31 μs, which is
calculated by (74.6 μs - 12.6 μs)/2; where 12.6 μs is the CircLink response time. This is equivalent to the
delay time of a 12-stage cascade connection HUB/CMI circuit.
(31μs / 2.5μs = 12.4 -> 12-stage)
If the sum of cable delay and HUB/CMI delay is over 31 μs, set ET1 to 0 to extend the response timeout
time to 298.4 μs, which is four times longer than the normal delay time. Taking this measures, the one way
propagation delay time is extended to (298.4 μs – 12.6 μs) /2 = 142.9 μs. (142.9μs / 2.5μs = 57.2 -> 57-
stage).
The timer can be set by the ET1 pin or internal register and has a structure of AND logic in the CircLink as
shown below.
Remarks:
Typical time delay added in the ON state HUB is 0.5 μs. However, it is extended to 1.0 μs if the optical
mode is ON (nOPMD = L) and CMI is OFF (nCMIBYP = L).
Values in text and table are based on a 2.5 Mbps network speed. When CircLink operates at 1.25 Mbps,
the value should be doubled. When operating at 5 Mbps, the value should be half. To be precise, the
propagation delay time of the cable and the transceiver should also be added.
2 9 8 . 4 u S
7 4 . 6 u S
(default"1")
ET1 :Pin
ET1 :Register
DATASHEET
Id le T im e r
3 2 8 u S
8 2 u S
Page 58
C o n f ig u r a tio n T im e r
Peripheral Mode CircLink™ Controller
ET1
1 0 4 m S
5 2 m S
SMSC TMC2072
Datasheet