CT2565 Datasheet, PDF (13/31 Pages) Aeroflex Circuit Technology – CT2565 Bus Controller, Remote Terminal and BUS Monitor FOR MIL-STD-1553B

Mode Code Illegalization (Optional)
The word count and TX/RX pins will be latched
800ns (typ) after the falling edge of NBGRNT
(See Figure 13, RTU Command Word Handling).
Table 5 lists the CT2565 pins associated with
mode code illegalization. If the current command
is a mode code, LMC (pin 55) will go high. Mode
codes can be illegalized, using an external PROM
(<200ns access time recommended), by setting
ILLCMD low after the NBGRNT flag. This will set
the message error (status word) and illegal Mode
Code (BIT word) bits followed by transmission of
the status word. Using the method, mode
commands can be "auto-screened" without
interrupting subsystem operation. For a complete
list of mode codes, refer to Table 8.
Table 5 – Mode Code Illegalization
PIN # SYMBOL
DESCRIPTION
51
WC0
12
WC1
52
WC2
13
WC3
53
WC4
15
T/R
Word Count LSB
Word Count 1
Word Count 2
Word Count 3
Word Count MSB
TX/RX
Note: A word count field of all 0’s indicates 32 data words; all 1’s
= 31 words.
NBGRNT (42)
LMC (55)
WC_0-4 T/R (15)
ILLCMD (48)
INCMD (9)
BUSREQ (19)
BUSACK (59)
SOM (78)
D0 - D15
STATUS INPUTS
t1
t2
t3
VALID UNTIL NEXT VALID COMMAND WORD RECEIVED
t4
LATCHED UNTIL NEXT VALID COMMAND WORD RECEIVED
t5
t9
DBACCEPT, SSFLAG, SVCREQ, SSER and SSBUSY INPUTS
t6 t7
t8
CMD VALID
SYM DESCRIPTION
MIN
Illegalize
t1
t2
t3
t4
Legal
t5
t6
t7
t8
Status Inputs t9
NBGRNT pulse width
151
NBGRNT to LMC delay
500
LMC to WC-T/R latch
-
LMC to ILLCMD latch
-
NBGRNT to INCMD delay
-
BUSACK to SOM delay
-
SOM pulse width
-
CMD VALID setup
60
NBGRNT low to status latch
-
Note: Memory read/write signals CS, OE, and ADRINC remain static at logic "1".
TYP
-
-
200
-
1.0
166
166
-
-
MAX
181
667
-
333
1.5
-
-
100
3
LATCHED
UNITS
ns
ns
ns
ns
µs
ns
ns
ns
µs
Aeroflex Circuit Technology
Figure 13 – RTU Command Word Handling/Status Inputs
13
SCDCT2565 REV B 8/10/99 Plainview NY [phone]