hi-3717 QuickLogic Corp, hi-3717 Datasheet - Page 11

• Manufacturer Part Number: hi-3717
• Description: Single-rail Arinc 717 Protocol Ic With Spi Interface
• Manufacturer: QuickLogic Corp

FUNCTIONAL DESCRIPTION (cont.)
2. Test Mode
3. No Sync Detect Mode
In both the Flight Recorder Mode and the Test Mode, the HI-3717
uses a proprietary sync tracking and detection method which allows
multiple random false sync marks in the user data without
increasing the sync time.
Digital Loopback
Normal HI-3717 operation is with CTRL1<0> set to “0”. Setting it to
“1” places the part in digital loopback mode. In this mode the
analog line receivers are disconnected from the data samplers and
both output line drivers are placed in a high impedance state. The
output encoders are connected to input sampler / decoder. The
part may be verified by selecting the desired receive decode format
The first word stored in the Receive FIFO is available when
RXFSTAT<2>, RFEMPTY, is reset to “0”, which is 12-bit periods
(one word time) after INSYNC is set to “1”.
The HI-3717 remains in sync as long as the proper sync
sequence is maintained. INSYNC is reset to “0” when the next
expected subframe sync mark is not present. The HI-3717 will
initiate a new synchronization process at the next valid SYNC1
mark.
Once the part falls out of sync, the whole previous subframe
should be discarded.
In this mode the HI-3717 searches for any two subframe sync
marks in the correct sequential order and the exact starting time
for the sync mark. INSYNC is set to “1” when the third valid sync
mark is detected. The part must continue to detect each sync
mark in the correct order and with the correct starting time to
stay in sync.
This method reduces the time required to obtain sync to about 2
seconds typical and a worst case of 3 seconds.
In this mode, the INSYNC is set to “1” and all data is stored in
the Receive FIFO. Without sync detection, the Receive FIFO
just records the sequential bits, not words, from the bus. It is up
to the user to detect the sync marks and determine the word
boundaries in this mode.
Bi-Polar Return to Zero
Harvard Bi-Phase
FIGURE 6.
+10V
-10V
Data
+5V
-5V
LSB
ARINC 717 HBP & BPRZ Differential Input Signal Format
1
HOLT INTEGRATED CIRCUITS
0
1
HI-3717
1
11
with RSEL pin or CTRL1<0>, writing the transmit FIFO and
reading the receive FIFO. All status pins and registers reflect the
status of the loopback operation.
FIFO Status Pin Assignment Register, FSPIN
This register assigns the function of the external RFIFO and
TFIFO pins. The RFIFO pin reflects the state of one of the three
Receive FIFO status flags (RFFULL, RFHALF and RFEMPTY) in
the Receive FIFO Status Register, RXFSTAT. The TFIFO pin
reflects the state of one of two Transmit FIFO status flags (TFULL
or TFHALF) in the TFXSTAT register. Refer to the FSPIN Register
Description in Table 7 for register assignment details.
Word Count Utility Register, WRDCNT
The MATCH pin goes high when the HI-3717 is in the INSYNC
condition and the word count and subframe count matches the
value programmed in the Word Count Utility Register. Note: The
INSYNC pin is set to “1” when the second consecutive SYNC1
mark of the proper sync sequence is received. The Word Count
Utility Register and Match pin function can be used for the
standard ARINC 717 data rates and all of the expanded data rates,
except 8192 wps.
ARINC 717 RECEIVER
The input data stream for ARINC 717 can be one of two formats.
The main ARINC 717 bus to a Digital Flight Data Recorder (DFDR)
uses Harvard Bi-phase (HBP) encoding and the auxiliary output
bus to an Aircraft Integrated Data System (AIDS) uses Bi-Polar
Return to Zero (BPRZ) encoding as shown in Figure 6.
The HI-3717 has an independent ARINC 717 receive channel with a
selectable on-chip HBP analog line receiver for connection to the
main incoming ARINC 717 data bus or a BPRZ analog line receiver
for connection to an auxiliary data bus.
for the HBP inputs:
The ARINC 717 specification requires the following detection levels
0
1
STATE
NULL
LO
HI
0
1
DIFFERENTIAL VOLTAGE
+2 Volts to +8 Volts
-2 Volts to -8 Volts
0
NA
0
1
1
MSB