CT2578

CT2578 is for use in simple Remote Terminal applications without the need for a processor or software development.

CT2578 provides the complete protocol for a Remote Terminal, supporting all types of message transfers including all 15 mode codes, with comprehensive error checking. Error handling of data is not required by the subsystem.

The user interface is a 16 bit bidirectional highway with a few control lines. The low power transceivers CT2578 are capable of providing the output voltage required by MIL-STD-1760 and are powered by a +5V supply.

If sinusoidal (McAir) transceivers are required then the part number becomes CT2581. This is the only difference between CT2578 and CT2581.

A 32 word data buffer memory is used to store messages until validation is complete. Only validated messages are transferred to the subsystem at a rate of 500 nS per word. Data to be transmitted is transferred from the subsystem to this buffer memory at a maximum rate of 1 uS per word.

This data memory may be bypassed in the receive mode and data transferred to the subsystem on a word by word basis as it is being received. CT2578 has an optional RT wrap around capability. When WRAPEN is active, data received at subaddress 1E (30) remains stored in the data buffer memory (i.e. not transferred to the subsystem). If followed by a transmit from subaddress 1E the same data will be transmitted.

There is an option within CT2578 to reduce the response time in order to conform to other standards such as 1553A and McAir. In this mode subaddress 1F is allocated a normal subaddress with subaddress 00 reserved for mode commands.

Any message may be illegalized by applying an active low on the NME discrete status input. The Remote Terminal CT2578 will respond with the Message Error bit set in the status and not use the information received.

A hardware implementation of the 1760 checksum algorithm within the device may be enabled via signal NENCHK. When transmitting, the checksum word is inserted in the last word position, and when receiving, a valid checksum word will generate the open drain output (STATUS). The STATUS output may be hard wired to any of the discrete status inputs (e.g. Service Request), if CT2578 is also hard wired to the input NILLCMD the device will respond to a failed checksum with the selected status bit set and not use the data (i.e. not transfer the data to the subsystem).

In addition to the signal NVCR (valid command word received) which may be used to illegalize commands, a signal NHDR (header word received)CT2578  is available to the subsystem for verification of the 1760 message header.

The RT address lines are latched on RESET as required by 1760. If all six RT address lines go open circuit the store released signal (STREL) will go high.

CT2578 is packaged in a 119 pin grid array or 84 lead CQFP package.