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CT1820 View Datasheet(PDF) - Aeroflex Corporation

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CT1820 Datasheet PDF : 14 Pages
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RECEIVE CYCLE OPERATION
DECODER SHIFT CLOCK (DSC) (see Figure 5) operates at
the data rate (1MHz). When the DECODER recognises a
valid sync and two valid Manchester data bits , a receive
cycle is initiated. The new sync is indicated at the
COMMAND/DATA SYNC (C/D SYNC) output and the TAKE
DATA output goes low 2 . The C/D sync output will remain
in its valid state until a new sync is detected on a
subsequent word or until DECODER RESET (DEC RST) or
MRST goes low. A low at DEC RST or MRST causes C/D
SYNC to go low.
TAKE DATA remains low for 16 DSC periods during which
time the 16 serial data bits appear at the SERIAL DATA
OUTPUT (SDO). This data is simultaneously loaded into the
first-rank receive register. The low-to-high transition of
TAKE DATA makes the new data available at the output
of the second-rank receive register. This data remains
available until the next low-to-high transitions of TAKE
DATA. It is not reset or cleared by any other signals. This
data is applied to the D0 to D15 I/O bus by setting DATA
SELECT lines low.
After all data has been loaded into the receive registers, the
data is checked for odd parity. A low on VALID WORD (VW)
output , indicates successful reception of a word without
any Manchester or parity errors. For consecutive word
receptions, VW will go high again in 3 to 3.5μs. In the
absence of succeeding valid syncs, VW will return high in
20μs. A DEC RST (low) at any time will reset VW high.
All decoded commands, including RT ENABLE (address
recognition), BROADCAST and MODE CODE are enabled
internally by VW and remain valid only as long as VW is low.
For 8-BIT l/O subsystems (D0 tied to D8, through D7 tied to
D15), data may be extracted in 8 BIT bytes by selectively
activating DATA SELECT 1 and DATA SELECT 2.
For serial data systems, SERIAL DATA OUTPUT is available
at the DSC rate from 2 to .
.
OSC
012345
16 17 18 19 0 1 2 3 4 5
16 17 18 19
DATA IN
DATA IN
½ SYNC ½ SYNC 15 14 13
½ SYNC ½ SYNC 15 14 13
2
1
0
P ½ SYNC ½ SYNC 15 14 13
2
1
0
P ½ SYNC ½ SYNC 15 14 13
2
1
0
P
2
1
0
P
TAKE DATA
C/D SYNC
FROM PREVIOUS WORD
VALID FOR CURRENT WORD
VALID FOR CURRENT WORD
SDO
UNDEFINED
15
4
3
2
10
UNDEFINED
15
4
3
2
1
0
VW
FROM PREVIOUS WORD
DECODE COMMANDS
(see text)
SECOND-RANK REC’V
REGISTER CONTENT
NOT VALID
FROM PREVIOUS WORD
DATA SELECT
OPTIONAL–HIGH = TRISTATE HI-Z AT D0 TO D15
VALID
NEW DATA
NOT VALID
OPTIONAL–HIGH = TRISTATE HI-Z AT D0 TO D15
VALID
NEW DATA
12
34
Figure 5 – RECEIVE CYCLE TIMING
SCDCT1820 Rev F 4/10/08
8
Aeroflex Plainview
 

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