Texas Instruments Sympol SN65HVD96, User Manual

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V
CC
GND
B
A
D
R
1
2
4 5
6
7
8
DE
3
RE
SN65HVD96
B
A
D
|V
OD
|
passive active
A or B
B or A
R
|V
ID
|
passive active
Driver signaling (DE = high) Receiver detecting (RE = low)
V
CM
V
CM
| | < 0.5V |V | > 0.9V
OD OD
V
| | < 0.5V |V | > 0.9V
OD OD
V
Overview
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1 Overview
The SN65HVD96 is designed for error-free data transmission under wire-fault conditions. The receiver
provides correct output data whether the bus wires are connected normally or cross-wired. This feature is
known as symmetric-polarity ( Sympol™) and is auto-detected internally, so no intervention from the
controller or the operator is required (see
Figure 1 ).
Figure 1. Block Diagram and Sympol™ Signal States
Figure 1 shows that Sympol™ signaling is similar but not identical to CAN-bus signaling. Sympol™
transceivers only look at the magnitude of the differential bus voltage, |V
A
– V
B
|, not its actual polarity. At a
driver output, this voltage is called |V
OD
|, at a remote receiver input, it becomes |V
ID
|.
A Sympol™ bus state is known as passive when |V
A
– V
B
| < 0.5V, and it is active when |V
A
– V
B
| > 0.9V.
Similar to RS-485, Sympol™ transceivers can be used for point-to-point, multi-drop, or multi-point
networks. Current-limited differential outputs protect in case of driver contention on a "party-line" bus. High
receiver input impedance allows the connection of at least 32 nodes. The pin-out is identical to the
industry-standard SN75176 transceiver, thus allowing for a direct upgrade from RS-485 to Sympol™.
Note that Sympol™ signaling does not support the operation of Sympol™ transceivers together with
RS-485 or CAN transceivers in a mixed-transceiver type of network. Only Sympol™ transceivers are able
to communicate between another. However, it is possible to replace an entire RS-485 transceiver network
with Sympol™ transceivers while maintaining the same high-level network protocol without the need for
software changes.
2 EVM Set-up and Precautions
Figure 2 shows the schematic of the SNHVD96 EVM. The board mounts 13 BergStik headers from JMP1
to JMP14 (JMP5 is omitted) and two 3-pin terminal blocks, TB1 and TB2, supporting the device evaluation
for a wide range of system configurations.
• Pin 1 (EARTH) is a second ground pin that allows applying an external voltage between GND and
EARTH to simulate common-mode voltage conditions.
• Pin 2 (GND) shall be connected to the negative output or ground terminal of the PSU. This pin
represents the ground potential of the device-under-test and the entire EVM. It also connects to
various jumpers on the board.
• Pin 3 (VCC) shall be connected to the positive output of a regulated 5V power supply unit (PSU) as it
represents the positive supply voltage of the device-under-test and also connects to various jumpers
on the board.
2 Sympol™ Transceiver SLLU128A – June 2010 – Revised August 2010
Copyright © 2010, Texas Instruments Incorporated