参数资料
型号: BU-63925F0-190
厂商: DATA DEVICE CORP
元件分类: 微控制器/微处理器
英文描述: 2 CHANNEL(S), 1M bps, MIL-STD-1553 CONTROLLER, CDFP70
封装: CERAMIC, DFP-70
文件页数: 13/48页
文件大小: 405K
代理商: BU-63925F0-190
20
Data Device Corporation
www.ddc-web.com
BU-63825
C-02/06-0
Sp’ACE II stores the full 16-bit 1553 Command Word in the
fourth location of the RT message descriptor.
RT COMMAND ILLEGALIZATION
The BU-63825 provides an internal mechanism for RT com-
mand illegalization. In addition, there is a means for allowing the
setting of the Busy Status Word bit to be only for a programmed
subset of the transmit/receive/broadcast subaddresses.
The illegalization scheme uses a 256-word area in the BU-
63825’s address space. A benefit of this feature is the reduction
of printed circuit board requirements, by eliminating the need for
an external PROM, PLD, or RAM device that does the illegaliz-
ing function. The BU-63825’s illegalization scheme provides
maximum flexibility, allowing any subset of the 4096 possible
combinations of broadcast/own address, T/R bit, subaddress,
and word count/mode code to be illegalized. Another advantage
of the RAM-based illegalization technique is that it provides for
a high degree of self-testability.
ADDRESSING THE ILLEGALIZATION TABLE
TABLE 31 illustrates the addressing scheme of the illegalization
RAM. As shown, the base address of the illegalizing RAM is
0300 (hex). The Sp’ACE II formulates the index into the
Illegalizing
Table
based
on
the
values
of
BROADCAST/OWNADDRESS
ADDRESS,
T/R
bit,
Subaddress, and the MSB of the Word Count/Mode Code field
(WC/MC4) of the current Command Word.
The internal RAM has 256 words reserved for command illegal-
ization. Broadcast commands may be illegalized separately from
nonbroadcast receive commands and mode commands.
Commands may be illegalized down to the word count level. For
example, a one-word receive command to subaddress 1 may be
legal, while a two-word receive command to subaddress 1 may
be illegalized.
The first 64 words of the Illegalization Table refer to broadcast
receive commands (two words per subaddress). The next 64
words refer to broadcast transmit commands. Since nonmode
code broadcast transmit commands are by definition invalid, this
section of the table (except for subaddresses 0 and 31) does not
need to be initialized by the user. The next 64 words correspond
to nonbroadcast receive commands. The final 64 words refer to
nonbroadcast transmit commands. Messages with Word Count/
Mode Code (WC/MC) fields between 0 and 15 may be illegalized
by setting the corresponding data bits for the respective even-
numbered address locations in the illegalization table. Likewise,
messages with WC/MC fields between 16 and 31 may be illegal-
ized by setting the corresponding data bits for the respective odd-
numbered address locations in the illegalization table.
The following should be noted with regards to command
illegalization:
(1) To illegalize a particular word count for a given broadcast/own
address-T/R subaddress, the appropriate bit position in the
respective illegalization word should be set to logic 1. A bit value
of logic 0 designates the respective Command Word as a legal
command. The BU-63825 will respond to an illegalized non-
broadcast command with the Message Error bit set in its RT
Status Word.
(2) For subaddresses 00001 through 11110, the “WC/MC” field
specifies the Word Count field of the respective Command Word.
For subaddresses 00000 and 11111, the “WC/MC” field speci-
fies the Mode Code field of the respective Command Word.
(3) Since nonmode code broadcast transmit messages are not
defined by MIL-STD-1553B, the sixty (60) words in the illegal-
ization RAM, addresses 0342 through 037D, corresponding to
these commands do not need to be initialized. The BU-63825 will
not respond to a nonmode code broadcast transmit command,
but will automatically set the Message Error bit in its internal
Status Register, regardless of whether or not the corresponding
bit in the illegalization RAM has been set. If the next message is
a Transmit Status or Transmit Last Command mode code, the
BU-63825 will respond with its Message Error bit set.
WC4/MC4
0(LSB)
SA0
1
SA1
2
0
SA2
3
SA3
4
SA4
5
T/R
6
BROADCAST/OWN_ADDRESS
7
1
8
1
9
0
10
0
12
0
13
0
14
0
15(MSB)
DESCRIPTION
BIT
11
TABLE 31. ILLEGALIZATION RAM ADDRESS
DEFINITION
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