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BASIC I/O Setup

  • Analog/Digital
  • Addresses
  • Baud Rates
  • Protocol Handshake Types
  • Network Type Switch
  • Communication Verification

Hardware Error Codes

  • Hardware Watchdog

Sensor/Actuator I/O Wiring

  • Analog Inputs
  • Analog Outputs
  • Digital Inputs
  • Digital Outputs

BASIC I/O Hardware User Manual

Chapter 2c - BASIC I/O SETUP

BIO4, BIO8 and BIO16 (not AD) Products


SETUP

BASIC I/O setup is accomplished with a sequential display and pushbutton.Below is a diagram of the location of these components:

Figure 2-9 BIO Connectors, Switches, Indicators

Figure 2-9  Connectors, Switches, and Indicators

Unit type (digital or analog), Unit address, baud rate, and 2 or 4 Pass protocols are all pushbutton configurable and appear on the sequential display. After line power application and the performance of system diagnostics, there is a five second period during which these setup values may be changed. Changed values are automatically saved in non-volatile EEPROM.

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Analog/Digital

The BASIC I/O system must be configured to accept either Analog or Digital I/O modules. The current I/O type is displayed on the sequential display and is indicated by the character following the "U". The unit will display a "1" if the unit is configured as digital and a "2" if the unit is analog. This value is stored in EEPROM and need only be set once. The factory default I/O type is digital. Changing the BASIC I/O type is explained after the description of addresses, baud rates, handshaking, and network types.

Addresses

Each Host instruction includes an address made up of two hexadecimal characters  (00H to FFH ). This address determines which chassis is to execute the instruction being sent; all other chassis are to ignore the instruction. Each BASIC I/O chassis has a unique address. The factory default address is "00". Changing the address is explained after the description of baud rates, handshaking, and network types.

Baud Rates

Any one of the standard baud rates of 300, 600, 1200, 2400, 4800, 9600, 19200, or 38400 can be used for the serial network communication. The sequential display indicates the letter H followed by the baud rate divided by 100. BASIC I/Os are shipped at 9600 baud; the sequential display indicates H096. Changing the Baud rate is explained after the description of handshaking and network types.


Protocol Handshake Types

Two protocol handshake types are available, 2 Pass and 4 Pass.

2 Pass: The Host transmits an instruction to a BASIC I/O.

If the instruction is correctly received (i.e. valid address, instruction type and correct checksum), the BASIC I/O executes the instruction and returns the letter A and a CR or, where data is to be returned, the letter A then the data followed by a two character checksum and ending with a CR.

4 Pass: The Host transmits an instruction to a BASIC I/O.

If the instruction is correctly received (ie valid address, but not necessarily the correct instruction type nor checksum), the BASIC I/O returns an A, followed by the echo of the instruction and does not execute it.

If the Host then transmits an E, the instruction is executed in the same manner as 2 Pass. If the Host transmits any other character to any unit on the network, the instruction is disregarded.

The sequential display indicates the letter P followed by 2 or 4.

BASIC I/Os are shipped in 2 Pass mode; the sequential display indicates P2. The actual setting of the Handshake Protocol Type is detailed following network type switch.

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Network Type Switch

Based upon the selected network configuration, each BASIC I/O must be setup before communication can begin. This is done with the network switches shown below. The three basic communication connections for individual BASIC I/Os are:

L1 Repeater

Used in RS-422 networks to extend range
to 5000 feet between units.

Network Switches

L2

Multidrop

Used in RS-422 or RS-485 networks.
Provides a total network range of 5000 feet.

L3

Last Unit

Must be used in RS-422 and RS-485 networks
for the unit most distant from the Host.

If there is only one BASIC I/O in a network it is designated L3.

For the network layout, the sequential display indicates the letter "L" followed by "1", "2", or "3". As shipped, BASIC I/Os are setup as "L3", Last Unit. This parameter is not changed by push button but is displayed as "L1", "L2", or "L3" after the dip switches have been set and the unit has undergone a power cycle.

When the unit is configured for "L3" a "Network Termination Resistor" is placed across the differential receiver. A value of 150 ohms was selected to suit most applications. A detailed analysis of transmission line effects (reflections), which is beyond the scope of this document, would be necessary to select the ideal termination resistor for any given application.

If the customer wishes to terminate the communication bus externally (at the terminal block location) then it is  imperative that no BASIC I/O network switches be set to "L3".

EIA standards dictate that the total bus impedance for RS-485 can be no less than 60 ohms.

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Setup Via Pushbutton

The pushbutton, located on the logic board (see Figure 2-9) is used to configure the unit address, baudrate, and network pass type.

During the diagnostic test period following the application of power, the sequential display shows  Go Go Go Go Go = .

Pumping the pushbutton once while the = appears, places the unit in the setup mode.

The BASIC I/O then flashes U 1 0 0 H 0 9 6 P 2    (The underlined values represent setup parameters that can be changed)

The digit following the U represents whether the unit is analog or digital where 1 indicates digital and 2 indicates analog. Initially this is set to 1 for digital operation.

The next 2 digits indicate the unit address; initially set to address 00H

The 3 digits after H is the baud rate divided by 100; initially set for 9600 Baud.

The 1 digit after P is the handshake protocol type; initially set for 2 Pass.

The value of each setup character can be changed, as they appear in sequence, by  pumping the pushbutton LED. As the button is pressed, the display will cycle through the possible values for each character. When the desired character is displayed simply wait a brief period for the display to blank. The next character position to be changed will then appear on the display.

The display continues to cycle through until there is a cycle with changes. The BASIC I/O then stores all values in EEPROM for automatic use following subsequent power cycles. The unit is now in the operational mode and the sequential display cycle becomes:

U 1 = 0 0  H 0 9 6  L 3  P 2

(The underlined values represent setup parameters that can be changed)

If any desired changes were not completed, line power can be recycled and the setup via pushbutton procedure can be repeated as required.

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Communication Verification

Most startup problems are related to the communication link. The installer is urged, after both the communication wiring and configuration have been completed, to test the network before installing I/O modules.

To test the serial communication link, the Host transmits the abbreviated test instruction: >NNA?? for each BASIC I/O address in the network, where NN is the address of each BASIC I/O. This appears on the Sequential Display after the U1 or U2.

Both the Host and the BASIC I/O under test are used to verify wiring, system configuration and operation. If the addressed unit returns an A, acknowledgement, the communication link is operational and the selected address is correctly configured. All Addresses in the network should be tested by the same means.

If the A acknowledgement is not returned, the behavior of the two Network traffic LED displays should be investigated.

The left LED (marked RECV) should blink on every BASIC I/O when the Host transmits an instruction. This should occur regardless of baud rate. If there is no indication of network traffic, the failure can be anywhere from the Host's hardware or software to the BASIC I/O. Generally the failure of the receive light to blink when the Host transmits can be attributed to faulty communication wiring. Locating the cause of failure should start at the Host end.

The right LED (marked TRANS) blinks only when the addressed BASIC I/O responds to a Host instruction. If the TRANS LED blinks, but the Host does not receive an A acknowledgement, the return circuit is suspect.

If an instruction is sent to the BASIC I/O and the RECV LED flashes but TRANS LED does not flash in response, first verify that the baud rate and unit address are correct. If both are correct, disconnect the wires attached to the "TO PRIOR + and -" terminals and resend the command.

If the BASIC I/O TRANS LED still does not flash in response to a host instruction contact duTec  (800-248-1632) for service.

If the BASIC I/O TRANS LED does flash in response to a host instruction, the return circuit from the to the Host should be verified. If this test is not successful the Host's receiving hardware and software should be tested.

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Hardware Error Codes

When the BASIC I/O is initially powered up, it goes through an internal self test. If any of the self-diagnostics fail, the unit will display an appropriate error code on the sequential display, and halt.

ERROR CODE 3:

If a solid 3 appears in the sequential display, recycle power without touching the pushbutton. This does not mean there is a problem, it means it is in factory test mode. Recycle power WITHOUT holding down the pushbutton.

OTHER ERROR CODES:

If 0,1,2,4,6, or 7 appear on the sequential display permanently there is a problem. Recycle power. If that does not resolve the error condition, please contact duTec (800) 248-1632.


HARDWARE WATCHDOG:

The hardware watchdog acts automatically in the event of a hardware or firmware failure and responds within one second. The hardware watchdog turns all outputs off, and resets the BASIC I/O. Do not confuse this with the programmable communication watchdog delay instruction.


FUSES:

A plug-in 5 amp, UL rated, fuse is installed between the minus field terminal and the I/O module. These fuses are generally only needed to protect output modules. Optional fuse values are available for special output protection requirements. Fuses are installed in sockets located on the module board next to the module. Thermocouples and RTD inputs do not utilize the Terminal Block and therefore do not make use of the fuse.

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Sensor / Actuator I/O Wiring:

Analog or digital modules can be placed at any module position. However, it is good practice for noise pickup, debugging and maintenance reasons to group and wire similar module types together. For minimum crosstalk between input and output wiring, input modules should be located at one end followed by output modules.

Modules should NEVER be installed or removed while power is applied to the BASIC I/O. Following insertion in their respective sockets, modules should be secured with the captive screw.


ANALOG INPUTS

Note: Analog modules normally run hot to the touch.

Correct polarity connections are essential to proper operation of all analog inputs. Connections to terminals marked with a "+" must be more positive than the terminals marked with a "-". Thermocouples and RTDs are connected directly to the modules with special connectors which insure correct polarity.

Analog input module status indicators are ON dimly, when input modules are installed, wired correctly, and their input signal is within the modules valid range. If these conditions are not met, the indicator light may be ON brightly, OFF , or may flicker.

The wiring and operation of analog input modules can be verified by the Host issuing a Configure as Input instruction, Setup H , followed by a Read Input Value instruction, Analog L. See the Software Protocol Manual, or Quick Reference Card for instruction details.

Figure 2-10, Figure 2-11, and Figure 2-12 show the wiring for various sources of analog inputs. With the exception of thermocouples and RTDs, connections are made via the black terminal strip. In the case of thermocouples and RTDs, mating connectors are included. There must be nothing connected to the screw terminals corresponding to these module positions. The source of analog input voltage or current is external to the BASIC I/O with the exception of ITP590, ITP590-1, ITR100 and ITR100-1.

Figure 2-10 AC Current and Voltage Wiring

Figure 2-10  AC Current and Voltage Wiring

Figure 2-11 Analog Voltage and Current Input Wiring

Figure 2-11  Analog Voltage & Current Input Wiring

Figure 2-12 Temperature Input Wiring

Figure 2-12  Temperature Input Wiring

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ANALOG OUTPUTS

Modules should NEVER be installed or removed while power is applied to the BASIC I/O. Following insertion in their respective sockets, modules should be secured with the captive screw. Correct polarity is essential to proper operation.

Note: Analog modules run hot to the touch.

Both voltage and current output modules provide their own isolated power output. This eliminates the need for external power supplies and insures electrical isolation between each output. This also makes it possible to wire voltage outputs in series to obtain larger voltage swings.

The wiring of analog output modules can be verified by the Host issuing a Configure as Outputs instruction, Setup I, followed by a Set Output Level,  Analog J instruction. See the Software Protocol Manual, or Quick Reference Card for instruction details.

Module status indicators for analog outputs blink briefly as outputs are updated. It should be noted that the status indictor only follows the logic instruction to the modules and does not show that the module or it's fuse is present. Outputs can only be verified by observing the output device, or by a multimeter or oscilloscope measurement.

OI420 analog output modules provide the current into loops with total resistance less than 275 ohms. If the loop resistance exceeds 275 ohms, an external power supply must be added to the loop as shown in Figure 2-13. Correct polarity is essential. The added voltage should be a nominal 1 volt for each added 50 ohms of loop resistance in excess of 275 ohms. The total added voltage can be up to 5 volts larger than the nominal calculation without damage. The voltage regulation of the added supply can be as poor as ± 10% without affecting accuracy.

Figure 2-13 Analog Voltage and Current Output Wiring

Figure 2-13  Analog Voltage and Current Output Wiring

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DIGITAL INPUTS

Modules should NEVER be installed or removed while power is applied to the BASIC I/O.

With the exception of IDC5S digital input modules, input sensing current comes from a source external to the BASIC I/O. IDC5S input modules provide their own current for sensing contact closures; they can be destroyed if an external source is connected.

The IDC5 and IDC5B input modules are polarity sensitive and operate only when the "+" terminal is more positive than the "-" terminal. Polarity does not affect the performance of IAC5, IAC5A or IDC5S input modules.

Because the field sides of input modules are totally isolated from each other, like polarities can be wired common to make use of a single power supply.

The wiring and operation of digital input modules can be verified by closing the individual input sensing contacts and observing the change on the Module status indicators. They are ON when the module input circuit is energized. Their wiring and operation can also be verified at the Host by issuing a Configure as Inputs instruction, Setup H, followed by a Read All Modules instruction, Digital M. See the Software Protocol Manual, or Quick Reference Card for instruction details.

 

Figure 2-14  Digital Input Wiring

Figure 2-14  Digital Input Wiring

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DIGITAL OUTPUTS:

Modules should NEVER be installed or removed while power is applied to the BASIC I/O.

The power for ODC5, ODC5A, OAC5 and OAC5A digital output modules comes from a source external to the BASIC I/O.

Because they contain a protective reverse diode, the ODC5 and ODC5A output modules are polarity sensitive and operate correctly only when the "+" terminal is more positive than the "-" terminal.

A digital output module connected backward conducts current through its protective diode and appears to be uncontrollable; it is !

Polarity does not affect the performance of OAC5 and OAC5A digital output modules.

Because the field sides of output modules are totally isolated from each other, like polarities can be wired common to make use of a single power supply.

The wiring of digital output modules can be verified by the Host issuing a Configure as Output instruction, Control I, followed by an Output ON/OFF, Digital J instruction. See the Software Protocol Manual, or Quick Reference Card for instruction details.

The module status indicator should follow the instruction. It should be noted that the status indictor only follows the logic instruction to the modules and does not show that the module, its fuse or that external power is present. Outputs can only be verified observing the output device, or by a multimeter or oscilloscope measurement.

Figure 2-15 Digital Output Wiring

Figure 2-15  Digital Output Wiring


This concludes duTec's BASIC I/O Hardware Manual. If you need further documentation or answers, please contact us at 800-248-1632, or e-mail support@dutec.net

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