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CT2578-12-QM-F84 View Datasheet(PDF) - Aeroflex Corporation

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CT2578-12-QM-F84
Aeroflex
Aeroflex Corporation Aeroflex
CT2578-12-QM-F84 Datasheet PDF : 22 Pages
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GENERAL DESCRIPTION
CT2578 is for use in simple Remote Terminal applications
without the need for a processor or software development.
It 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 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.
The device 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 the device 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 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 it 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) 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.
The device is packaged in a 119 pin grid array or 84 lead CQFP
package.
SIGNAL DESCRIPTIONS
1553 / 1760 DATA BUS
DATABUS 0
Signal is connected to the positive side of the external data bus
transformers for bus 0.
NDATABUS 0
Signal is connected to the negative side of the external data bus
transformers for bus 0.
DATABUS 1
Signal is connected to the positive side of the external data bus
transformers for bus 1.
NDATABUS 1
Signal is connected to the negative side of the external data bus
transformers for bus 1.
HARD WIRED
ADDR A-E (Inputs with pull up resistor)
Remote Terminal address inputs for the unit. ADDR A is the
least significant bit and ADDR E is the most significant bit.
These inputs are internally latched every time the unit is reset.
The latched address information is then compared to the
incoming command word.
ADDR P (Input with pull up resistor)
Parity bit for the Remote Terminal address inputs. ADDR P
must be set to ODD parity. This input is latched as above.
WRAPEN (Input with pull down resistor)
Select Remote Terminal wrap around to subaddress 1E. The
Bus Controller sends data to subaddress 1E which remains in the
data buffer memory and is available to be sent back on the very
next command by the Bus Controller. The data in the data buffer
memory in this mode does not get transferred to the subsystem.
If the very next command is not a transmit command to
subaddress 1E, the data buffer memory is flushed and will
respond normally to the next set of commands. If the wrap
around test is enabled, data to subaddress 1E must be transferred
in the correct sequence.
“0" = Normal mode
“1" = Wrap Around mode
MCAIR (Input with pull down resistor)
This signal sets the unit to respond with a status word within
4 uS (dead bus time). Subaddress 1F is also enabled to be a valid
subaddress for data. Normally subaddress 00 and 1F are
reserved for mode codes.
“1" = 4 uS dead bus response time, subaddress 1F used for data.
“0" = 12 uS response time, subaddress 1F used for mode codes.
C16MHZ (Input with pull up resistor)
Free running 16 MHZ clock input.
SUBSYSTEM INTERFACE
T0-T15 (Bibirectional IO)
16 bit bidirectional highway to transfer all information to / from
subsystem. The user can also utilise this bus to monitor
Command word and Header word (1760 requirement) for
message illegalization.
SCDCT2578 REV B 3/11/98
2
 

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