Twinax Cable Information
Index
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The following guidelines can be used for testing line continuity and polarity (twinaxial cable only). The tests should be made for individual cable segments. However, they may be used for a complete cable if the station junctions are connected via an adapter (like a "Smart-T" connector) or an Anzac backpanel unit which has the "Cable Thru" feature (if the power is off). Measurements are not valid with station protectors connected to the line.
Line Continuity
The only tools required for line continuity checks are an ohmmeter and jumpers to connect between the connector pins (signal lines) and the connector body (cable shield). When the following checks are made, the resistance values measured should fall within the indicated ranges (for the maximum 1525 meters/5000 feet when twinaxial cable is used, and 610 meters/2000 feet when coaxial cable is used).
Twinaxial Cable:
With both ends of the cable open and the cable not plugged into a machine, measure (at either end):
A reading of less than 1,000,000 ohms means that there is a short in the cable.
With both ends tied to the shield at the far end, measure (at the nearest end):
A reading greater than 110 or 70 ohms, respectively, means that there is an "open."
Coaxial Cable:
With both ends of the cable open and the cable not plugged into a machine or a twinaxial-coaxial adapter, measure the shield to conductor resistance. It should be greater than 1,000,000 ohms.
Line Polarity (Twinaxial Cable only)
After testing the line continuity and making any necessary corrections, check the polarity as follows:
The polarity of the line must be maintained for each cable segment and for the entire cable run to ensure proper machine operation.
The Anzac interface and the host controller communicate through the twinax cable, which is half-duplex. The interface takes the differential signal from the controller and translates it in to a meaningful digital signal which is serially received by shift register xx. Also, the digital poll responses of the interface are translated into a differential signal and sent back to the controller through the same twinax line.
The bit stream contains the bit frame sync pattern, and a frame. The bit/frame sync pattern establish synchronization between the interface and the controller, and are transmitted prior to the transmission of the first frame. A bit sync pattern has a half-bit binary configuration of 1010101010, and the frame sync pattern has the configuration of 111000. The frame is the basic unit of information used to transmit all data, commands, and status between the printer and the controller.
Each frame is 16 bits numbered from 0 to 15. The first bit that gets transmitted is bit 15 which is the start bit and is always 1 as it is shown in Figure 2. The bit description is as follows:
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Start Bit |
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Start Bit |
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This is the actual byte of information transmitted or the status of the printer received by the controller. |
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These bits represent the address of the printer unless they are all set which indicates the end of the message. |
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Makes even parity for bits 3 through 15 |
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These are frame bits. Always set to 000. |
The interface to the printer is a digital interface. A bi-phase technique is used for encoding on the cable. The commands sent through the twinax line are either commands sent by the controller or the poll responses sent by the printer.
The printer will never initiate a transaction to or from the attaching controller. All such transactions are explicitly initiates from the attached controller via a command. The following are valid commands for the printer:
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Read Status, Read ID, and Write Data must be followed by an activate command. All command frames must be preceded by a line turnaround (the bit/frame sync).
This command is sent from the controller to the printer and initiates the transfer of one or two status frames depending on whether or not a Set Mode command has been received.
Bit 7 should be 0, Bit 8 is used to acknowledge and reset the line parity from the interface. This bit is only effective when the not busy signal is received by the controller. If bit 9 is set, then all non-real-time poll response bits are updated, and the "poll response level" bit (14) is inverted.
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Bit Map of the Poll Command
The first response frame is always preceded by the bit and frame synchronization. Two-framed response is made to poll commands after the set mode command is received. Before the Set Mode command, the interface will respond with single frame to the controller's poll command.
From the time that the controller sends the last byte of the poll command, the printer has 60 microseconds (+/-30) to send the response. If the response is not received within this period, the controller discontinues communication.
The second frame of the poll response is sent after the full delay specified by the controller during the Set Mode command.
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Bit Map of the Byte 1 of Poll Response
Bit definition is as follows:
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When bit 10 is set, outstanding status is available and should be obtained by using Read Status command.
Bit 14 is changed only when the controller allows level transitions to occur by setting the ACK bit in the poll command. If no level change is requested by the controller, the odd status will be re-transmitted by the interface. Real-time status bits are not affected by response level transition.
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Last Message |
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Bit Map of Poll Response Byte 2
The following is the definition of bit map of second poll response:
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| Return To Twinax Cable Info. Index |
These are the commands sent to the printer by the controller.
| Command | Definition |
| Write Data Command | Causes all of the data after Write Activate to be stored in the printer, if the printer is not busy. Maximum data size is 256 bytes. |
| Write Control Data | Bit 13 resets exception condition; Bit 14 resets the outstanding status. |
| Activate Write | This command is inserted between Write Data and data frames. It also resets the print completed bit. |
| Activate Read | This command comes between Read Status or Read ID and the specified response. |
| Set Mode | This command determines the number of zeros between each frame. This number is in the frame immediately following and is less than 31 (decimal). |
| Read Status | This command causes the transfer of one frame of data from the printer to controller (preceded by a frame sync) containing the condition of the printer (after receiving the Read Activate command). |
| Reset | Causes the printer to go busy |
| Clear | Causes the printer to go busy |
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