HI-6120 HOLTIC [Holt Integrated Circuits], HI-6120 Datasheet - Page 49

• Manufacturer Part Number: HI-6120
• Description: MIL-STD-1553 Remote Terminal ICs
• Manufacturer: HOLTIC [Holt Integrated Circuits]

the fixed address range of 0x0100 to 0x01FF. See Fig-
ure 4. The table is comprised of 256 16-bit words. To
cover the full range of 1 to 32 data words, each subad-
dress uses a pair of illegalization registers. The lower
register (even memory address) covers word counts 0 to
15, using one bit per word count. As in command encod-
ing, “0” denotes 32 data words. Bit 0 corresponds to 32
data words, bit 1 corresponds to 1 data word and bit 15
corresponds to 15 data words. The upper register (odd
memory address) similarly covers word counts 16 to 31,
using one bit per word count. Bit 0 corresponds to 16
data words, while bit 15 corresponds to 31 data words.
When a command’s subaddress field equals 0 or 31
(0x1F), the command is a mode command. Table en-
tries for mode commands use bits to represent mode
code numbers, not word counts. The lower register
(even memory address) covers mode codes 0 to 15, us-
ing one bit per mode code. Bit 0 corresponds to mode
code 0, bit 15 corresponds to mode code 15. The upper
register (odd memory address) similarly covers mode
codes 16 to 31, using one bit per mode code. Bit 0 cor-
responds to mode code 16, bit 15 corresponds to mode
code 31. There is no functional difference between SA0
mode commands and SA31 mode commands. Since
either subaddress indicates a mode command, the sub-
address 0 table words should match the subaddress 31
table words in each quadrant.
Table entries from 0x0142 to 0x017D do not have to be
programmed. These correspond to broadcast transmit
subaddress commands (undefined by MIL-STD-1553B)
and are always invalid. There is no terminal response.
Addressing for the Illegalization Table is derived from
the command word T/R bit, subaddress field, MSB of
the Word Count (Mode Code) field and the command’s
broadcast vs. non-broadcast status as shown below in
Figure 4.
Address From the Received Command Word
Figure 4. Deriving the Illegalization Table
Bit Fields Comprise Each Received Command Word
0 0 0 0 0 0 0 1
Command
Sync
TA4:0 = 11111
Terminal
Address
else “1”
TA4:0
“0” if
T/
Bit
R
Subaddress
SA4:0
(Mode Code)
Word Count
WC4:0
Table
Address
HOLT INTEGRATED CIRCUITS
HI-6120, HI-6121
P
49
Figure 6 shows individual bit locations in the Illegaliza-
tion Table for broadcast and non-broadcast variants of
all mode commands defined by MIL-STD-1553B. Loca-
tions are also identifed for reserved mode codes and
undefined mode code commands.
The following examples illustrate how the Illegalization
Table is initialized to distinguish between legal and il-
legal commands when “illegal command detection” is
being used. Remember: If the terminal does not use il-
legal command detection, the table is left in its post-MR
reset state, with all table locations reset to 0x0000. In
this case, all command responses are “in form”.
For “subaddress commands” (ordinary receive com-
mands or transmit commands) individual table bits cor-
respond to word counts specified in the received com-
mand word. If a bit is 0, the corresponding word count is
legal. If a bit is 1, the corresponding word count is illegal.
For example, transmit commands to subaddress 1 are
controlled by the words at 0x01C2 and 0x01C3. In Fig-
ure 5, these words are located in the “RT Address Trans-
mit” block. The word stored at 0x01C3 controls subad-
dress 1 transmit commands having word counts 16 to
31. The word stored at 0x01C2 controls subaddress 1
transmit commands having word counts 1 to 15 or 32.
(Reminder: In MIL-STD-1553B, zero corresponds to 32
words.)
Word at 0x01C3 (Tx Subaddr 1) 31 to 16 words
Bit
Words
Word at 0x01C2 (Tx Subaddr 1) 15 to 1 & 32 words
Bit
Words
If the word stored at 0x01C3 = 0xFFFF and the word
stored at 0x01C2 = 0xFF0F, then commands with 4, 5,
6, or 7 data words are the only legal transmit commands
for subaddress 1 and all other word counts are illegal.
Receive commands and broadcast receive commands
for Subaddresses1 through 30 are encoded similarly.
For “mode code commands” (characterized by com-
mand word subaddress field equal to 00000 or 11111 bi-
nary) individual table bits correspond to individual mode
code values. Here “transmit” and “receive” simply indi-
cate the state of the command word T/R bit. (For mode
codes 0-15, the T/R bit does not indicate data direction
since data is not transacted when fulfilling these com-
mands).
15 14 13 12 11 10
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
15 14 13 12 11 10
15 14 13 12 11 10
9
9
9
8
8
8
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1 32
0
0