HI-6121PQMF HOLTIC [Holt Integrated Circuits], HI-6121PQMF Datasheet - Page 27

• Manufacturer Part Number: HI-6121PQMF
• Description: MIL-STD-1553 Remote Terminal ICs
• Manufacturer: HOLTIC [Holt Integrated Circuits]

COMMAND RESPONSES, Cont.
A “valid command” can be specifically addressed to the
individual HI-6120 terminal (the command word’s
embedded Terminal Address field matches the terminal
address latched in the Operational Status register) or can
be a “broadcast command” addressed to all terminals.
Broadcast commands are always addressed to RT
address 31 (0x1F). In systems where broadcast
commands are disallowed, RT31 is not used as a
conventional terminal address. When set, the BCSTINV bit
in Configuration Register 1 renders RT31 commands as
“invalid”: broadcast commands are indistinguishable from
commands addressed to other terminals. Invalid
commands are simply disregarded.
When the command word’s 5-bit SA (subaddress) field is in
the range of 1 to 30 (0x01 to 0x1E) the command is
considered a “subaddress command”. The terminal will
either receive or transmit data words, and “direction” is
specified by the command’s
words transacted is specified in the 5-bit word count field,
ranging from 1 to 32 words. Thirty-two data words is
represented when the word count field equals 0x00.
When the command’s 5-bit subaddress field equals 0 or 31
(0x1F) a “mode code” command is indicated; the low order
five bits no longer specify a word count, instead they
convey a mode code value. This data sheet refers to mode
code commands by the mode code number. For example,
a mode command with 5-bit mode code field of 0x10 is
called MC16, and the full range of mode code values is
MC0 through MC31 (decimal).
Mode codes MC16 through MC31 (0x10 through 0x1F)
have a single associated data word. When the command
T/
command word and received by the RT. When the
command’s
by the RT, following the terminal’s transmitted status word.
Mode codes MC0 through MC15 (0x0F) do not have
associated data words. For these 16 commands, the
command
commands must be transmitted with
the
Twenty-two mode commands are “undefined mode
R
T/
bit equals 0, the data word is contiguous with the
R
Command
bit is 0, the mode command is “undefined”.
Sync
T/
T/
R
R
bit does not specify “direction”. These
bit equals 1, the data word is transmitted
Terminal
Address
Field
T/
T/R
Bit
R
FIGURE 2. MIL-STD-1553 Command Word Structure
Subaddress
bit. The number of data
(SA) Field
T/
R
bit equal to 1. If
HOLT INTEGRATED CIRCUITS
Word Count
Field *
HI-6120, HI-6121
Parity
Bit
27
commands ” in MIL-STD-1553B:
The UMCINV bit in Configuration Register 1 determines
how these undefined mode commands are handled by the
HI-6120. If the UMCINV configuration bit equals 1, the
undefined mode commands are treated as invalid. They
are not recognized by the device. There is no terminal
response and status is not updated. If the UMCINV
configuration bit equals 0, the 22 undefined
commands are considered valid; this is the default
condition following reset. For this case, terminal response
depends on whether or not the application uses “illegal
command detection:”
If
Illegalization Table entries should be logic 0, including the
22 entries for these undefined commands. (The
Illegalization Table is fully described later in this data sheet.
After MR reset, all entries equal logic 0.) The terminal
responds “in form”, transmitting clear status (and a single
mode data word if the command is MC17, MC20 or MC21
with
If
Table entries for these 22 undefined commands should be
initialized to logic 1. In this case, the terminal will respond
with status word only, with Message Error bit set. No mode
data word is transmitted. Terminal status is updated.
Twenty-seven mode codes are considered “reserved” in
MIL-STD-1553B:
Treatment of these reserved mode commands depends on
their respective Illegalization Table entries. As described
above for undefined mode commands, response depends
on whether or not illegal command detection applies.
Any mode commands not implemented in the HI-6120
terminal should be treated the same as reserved mode
illegal command detection applies
illegal command detection is not used
* Word Count field is replaced by Mode Code
T/
field when the SA field equals 0x00 or 0x1F
R
Mode Codes 0 through 15 with
Mode Codes16, 18 and19 with
Mode Codes 17, 20 and 21 with
Mode Codes 9 through 15 with
Mode Codes 22 through 31 with
Mode Codes 22 through 31 with
bit = 1). Terminal status is updated.
T/
T/
T/
T/
, the Illegalization
T/
T/
R
R
R
R
R
R
bit = 0
bit = 1
bit = 0
bit = 1
bit = 1
bit = 0
mode
, all