UM0378
User manual
JTAG opto-isolation board
Introduction
The JTAG opto-isolation (AI-JTAG/OPTO-1) board can be connected between development
tools and an application board to provide electrical isolation. This is essential when the
development tools are not connected to the same ground as the application. It is also useful
to protect the development tools from electrical spikes that often occur in some applications,
such as motor control applications.
The JTAG opto-isolation board can be used with any tools that use the 20-pin JTAG
standard connection for in-circuit debugging and programming of ST ARM core-based
microcontrollers.
Figure 1.
JTAG opto-isolation board
Features
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1kV DC isolation
Supports 3.3V or 5V operation, configurable by solder bridge
Powered from target application using DC/DC converter powered by 3.3V or 5V
JTAG standard 20-pin connection supporting TRST, TDI, TMS, TCK, RTCK, TDO,
RESET signals
3.3V or 5V CMOS level compatibility
40nS maximum propagation delay for all unidirectional signals
Power consumption on target application power supply less than 200mA
February 2007
Rev 1
1/9
www.st.com
Hardware layout and configuration
UM0378
1
Hardware layout and configuration
The JTAG opto-isolation board uses high speed optocouplers that allow a very low
propagation time between input and output (typically 30nS). The board includes:
●
●
a JTAG standard 20-pin female HOST connector (J1) that allows direct connection of
the development tool,
a JTAG standard 20-pin male TARGET connector (J2) for connection of the application
board.
The opto-isolation board is delivered with a 7cm, 20-pin flat cable with JTAG standard
connectors to facilitate the connection to the application board.
The hardware block diagram shown in
Figure 2
illustrates the functional connections
between the development tool (HOST) and the application (TARGET).
Figure 3
will help you
locate main features on the JTAG opto-isolation board.
Figure 2.
Functional block diagram
RESET
RESET
TRST
TRST
TDI
TDI
TMS
TMS
TCK
TCK
TARGET Connector
HOST Connector
TDO
RTCK
RTCK
TDO
Power
supply
DC/DC
converter
For more detailed information on functional connections on the board, refer to
Figure 5 on
page 6,
and to
Figure 6 on page 7.
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UM0378
Figure 3.
JTAG opto-isolation board layout
Hardware layout and configuration
Optocouplers
J2
JTAG target
connector
J1
JTAG host
connector
LD1
Light on when
power on
TP6
3.3V/5V
jumper
G1
3.3V
configuration
G2
5V configuration
U14
DC/DC converter
MB535 REV.B
JTAG OPTO ISOLATION
TARGET
HOST
3/9
Power supply configuration
UM0378
2
Power supply configuration
The JTAG opto-isolation board is powered by the target application power supply available
on pin 1 and pin 2 of the J2 target connector. An isolated DC/DC converter on the board
provides the power supply for components on the host side of the board. When host and
target power supplies are present on board the LD1 LED is lit.
The board needs to be configured for 3.3V or 5V operation depending on the target
application voltage.
The voltage is configured using a solder bridge on G1 or G2.
●
●
G1 bridge ON/G2 bridge OFF: 3.3V configuration (default configuration)
G2 bridge ON/G1 bridge OFF: 5V configuration
Caution:
Components may be damaged if G1 and G2 are both configured ON.
If you need to change the power supply configuration frequently, it is possible to solder a 3-
position jumper in place of TP6 on the silkscreen (see
Figure 3).
If a jumper is implemented,
the G1 and G2 bridges must be OFF.
The voltage configuration with a jumper is shown in
Table 1.
Table 1.
Voltage configuration with jumper
3.3V configuration
(TP6 on pins 1 & 2)
5V configuration
(TP6 on pins 2 & 3)
1 2 3
1 2 3
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UM0378
JTAG connectors
3
JTAG connectors
Figure 4.
JTAG debugging connector (top view)
19 17 15 13 11 9 7 5
3
1
20 18 16 14 12 10 8 6
4
2
Table 2.
JTAG debugging connector (CN7)
Description
3.3V/5V power
TRST
TDI
TMS
TCK
RTCK
TDO
RESET#
DBGRQ
DBGACK
Pin number
2
4
6
8
10
12
14
16
18
20
Description
3.3V/5V power
GND
GND
GND
GND
GND
GND
GND
GND
GND
Pin number
1
3
5
7
9
11
13
15
17
19
4
Schematic diagrams
5/9
51mcu
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