EM120 Ethernet-to-serial Module
The EM120 is an Ethernet Module for onboard installation. Module hardware includes
one 10BaseT Ethernet port (standard Ethernet magnetics are NOT integrated into
the Module), one serial port (CMOS-level) with a number of additional generalpurpose I/O lines, and an internal processor, whose firmware acts as a bridge
between the Ethernet and serial ports. Ethernet "side" of the Module connects
directly to a standard Ethernet magnetics circuit (such as YCL-20F001N) or RJ45
connector with integrated magnetics. Serial "side" interfaces directly to the serial
port pins of most microcontrollers, microprocessors, UARTs, etc.
From the hardware standpoint, the EM120 can be viewed as a universal platform
suitable for running a variety of network and serial communications-related
applications. It is the application firmware, not hardware that gives the EM120 most
of its functionality.
The Application firmware EM120 is supplied with, currently in its 3rd generation
("Release3"), turns the EM120 into a Serial Device Server used to connect serial
devices to the Ethernet (TCP/IP) networks.
The application firmware of the EM120 can be upgraded through the module's serial
port or Ethernet port. Serial upgrades are facilitated by a so-called Monitor- a fixed
"service" firmware inside the EM120. The Monitor cannot be upgraded. Network
upgrades rely on the application firmware itself- there is a self upgrade algorithm
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that will be detailed later.
Since most of the EM120's operation is defined by its firmware the major part of
EM120's functional description can be found in the
Device Server Application Firmware Manual. This EM120 Ethernet Module Manual
focuses on the hardware portion of the EM120.
I/O pin 2.1.3.1
assignment and pin functions
Click on the pin in the diagram above or one of the links provided below to learn
more about EM120's I/O pins:
· Ethernet port lines
· Serial port and general-purpose I/O lines
· LED lines
· Power, reset, and mode selection lines
Ethernet port lines
#6
TX+
Output
Positive line of the differential output signal pair
#7
TX-
Output
Negative line of the differential output signal pair
#3
RX+
Input
Positive line of the differential input signal pair
#4
RX-
Input
Negative line of the differential input signal pair
Ethernet port of the EM120 is of 10BaseT type. Onboard electronics of the EM120
do not include Ethernet magnetics, so magnetic circuitry must be connected
externally. You can use either a standalone magnetics part (such as YCL-20F001N)
or RJ45 connector with integrated magnetics.
It is important to make the PCB wire connections between the Ethernet port pins of
the EM120 and external magnetics circuitry as short as possible. Making the wires
too long may cause the noise level generated by your PCB surpass the maximum
radiated emission limits stipulated by FCC and CE regulations. Additionally, longer
Ethernet lines on the PCB will make your board more susceptible to the damage from
the ESD (electrostatic discharge).
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Serial port and general-purpose I/O lines
#8
P8
Input/output
General-purpose input/output line
#9
P7
Input/output
General-purpose input/output line
#10
P6
Input/output
General-purpose input/output line
#11
P1
Input/output
General-purpose input/output line
#12
P0
Input/output
General-purpose input/output line
#15
Input/output
(output)
Input/output
(input)
#17
P3
(DTR)
P2
(DSR)
TX
General-purpose input/output line
Data terminal ready output
General-purpose input/output line
Data set ready input
Serial transmit line
#18
RX
#19
P4
(CTS/SEL)
Input/output
(input)
#20
P5
(RTS/DIR)
Input/output
(output)
#16
Serial receive line
General-purpose input/output line
Clear to send input
Full-/half-duplex selection input
General-purpose input/output line
Request to send output (full-duplex mode)
Data direction control output (half-duplex mode)
Line functions defined by the application firmware are shown in blue
The EM120 features a serial port (RX, TX lines) and several general-purpose I/O
lines (P0-P8). All of the above lines are of CMOS type. From the hardware point of
view, all general-purpose I/O lines can serve as inputs or outputs. Maximum load
current for all CMOS lines is 10mA.
Simplified structure of EM120's I/O lines is shown on the circuit diagram below. All
lines are "quasi-bidirectional" and can be viewed as open collector outputs with
weak pull-up resistor. There is no explicit direction control. To "measure" an external
signal applied to a pin the OUT line must first be set to HIGH. It is OK to drive the
pin LOW externally when the pin outputs HIGH internally.
The application firmware of the EM120 maps certain serial port functions onto the
general-purpose I/O pins- these functions are shown in blue in the table at the top
of this topic. For example, P5 is a universal input/output but the application
firmware can be set to turn this line into the RTS output of the serial port.
Therefore, depending on your application you can view P5 as a general-purpose I/O
line or specific control line of the serial port (RTS).
Being of CMOS type, the serial port and I/O lines of the EM120 can be connected
directly to the serial port pins and I/O lines of most microcontrollers,
microprocessors, etc. An interface IC* must be added to the EM120 externally if
you want to connect the module to a "true" serial port (for example, COM port of
the PC).
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Hardware Manuals
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Logical signals on the serial port lines of the EM120 are active LOW. TX and RX lines
are high when idle, start bit is LOW, stop bit is HIGH; LOW on CTS and RTS lines
means "transmission allowed" and HIGH means "transmission not allowed". This is
standard for CMOS-level serial ports and is exactly opposite to the signalling on the
RS232 cables. Logical signals on the EM120 are inverted because standard interface
ICs* invert the signals internally too.
As explained earlier, actual functionality of the I/O lines is firmware-dependent. See
serial port and serial communications for details.
* Such as MAX232 for RS232, MAX485 for RS485, etc.
LED lines
#1
EG
Output
Green Ethernet status LED
#2
EY
Output
Yellow Ethernet status LED
#21
L3 (SG)
Output
LED output 3, Green status LED
#22
L4 (SR)
Output
LED output 4, Red status LED
Line functions defined by the application firmware are shown in blue
The EM120 has four LED control lines. All lines have the same internal structure and
the LEDs should be connected to these lines as shown on the schematic diagram
below. Maximum load for each line is 10mA.
EG and EY lines reflect the status of the Ethernet port. The EG LED is normally ON,
and is temporarily turned off whenever the EM120 receives a network packet. The
EY is normally OFF, and is temporarily turned on whenever a data collision is
detected on the Ethernet.
SG and SR lines are under firmware control and display various status information
depending on what firmware is running at the moment. Follow the links below to
learn more about the behaviour of these LEDs under different conditions:
· SR/SG behavior in the monitor firmware.
· SR/SG behavior in the application firmware.
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Power, reset, and mode selection lines
#13
VCC
Positive power input, 5V nominal, +/- 5%, app. 50mA
#5
GND
Ground
#14
GND
Ground
#23
RST
Input
Reset, active high
#24
MD (MD)
Input
Mode selection pin
Line functions defined by the application firmware are shown in blue
The EM120 should be powered from a stabilized DS power supply with output
nominal voltage of 5V (+/- 5% tolerance). Current consumption of the EM120 is
approximately 50mA.
Proper external reset is a must! Reset pulse should be an active HIGH. We strongly
advise against using low-cost RC-networks and other unreliable methods of
generating reset pulse. Reset should be applied for as long as the power supply
voltage is below 4.6V. We recommend using a dedicated reset IC with brownout
detection, such as MAX810. Reset pulse length should be no less than 50ms,
counting from the moment the power supply voltage exceeds 4.6V.
If the EM120 is used to serve as a communications co-processor in a larger system
that has its own CPU it is also OK to control the RST line of the EM120 through a
general-purpose I/O pin of the "host" microcontroller. I/O pins of many
microcontrollers default to HIGH after the powerup and this means that the reset
will be applied to the EM120 at the same time when the host microcontroller is
reset. All the host microcontroller has to do is release the EM120 from reset at an
appropriate time by switching the state of the I/O line to LOW.
The MD line of the EM120 is used to select the operating mode of the EM120 and/or
its application firmware. The reason why the pin name is shown as MD(MD) is
because the functionality of this pin is in part hardwired and in part depends on the
application firmware:
· Hardwired functionality. When the EM120 powers up it verifies the state of the
MD input. If the MD input is at HIGH the EM120 proceeds to verifying and running
the application firmware loaded into its internal FLASH memory. If the MD input is
at LOW the EM120 enters the serial upgrade mode. For more information see
Monitor.
· Application firmware-dependent functionality. When the application firmware
is already running the MD line is typically used to make the EM120 enter the serial
programming mode. For more information see serial programming.
When the EM120 is used as a co-processor in a host system the MD line can be also
controlled by the host microcontroller. Ability to control both the RST and DS lines
allows the host microcontroller to switch between the operating modes of the
EM120.
©2000-2004 Tibbo Technology Inc.
Hardware Manuals
Mechanical
dimensions
2.1.3.2
L
Max.
35.0
Module length
W
Max.
27.5
Module width
H
Max.
9.1
Module height
I
Min.
5.0
Lead length
m
Max.
0.5
Lead "flash"
d
Aver.
30.0
Distance between lead rows
p
Aver.
2.0
Pin pitch
All dimensions are in millimeters
Specifications
2.1.3.3 and EM120 modifications
The EM120 has one submodel in circulation- EM120-00.
Device specifications are presented in the table below.
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Parameter
EM120-00
Ethernet interface
10BaseT Ethernet, magnetics not built-in
Serial interface and I/O lines
Routing buffers size
CMOS-level; TX, RX, and 9 additional I/O lines
with RTS, CTS, DTR, DSR implemented in
application firmware
12Kbytes x 2*
Maximum load current of I/O lines
10mA
Power requirements
DC 5V, +/- 5%, app. 50mA
Operating temperature
-10 to +70 degrees C
Operating relative humidity
10-90%
Mechanical dimensions (excl. leads)
App. 35x27.5x9.1mm
Packing
Plastic tray, 50 modules/tray
* Maximum possible buffer size. Actual size may be smaller depending on how
much RAM is "consumed" by the firmware