参数资料
型号: BU-61843G4-142Q
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, MQFP72
封装: GULL WING, PACKAGE-72
文件页数: 17/56页
文件大小: 321K
代理商: BU-61843G4-142Q
SINGLE BUFFERED MODE
The operation of the single buffered RT mode is illustrated in
FIGURE 6. In the single buffered mode, the respective lookup
table entry must be written by the host processor. Received data
words are written to, or transmitted data words are read from the
data word block with starting address referenced by the lookup
table pointer. In the single buffered mode, the current lookup
table pointer is not updated by the Enhanced Mini-ACE memory
management logic. Therefore, if a subsequent message is
received for the same subaddress, the same Data Word block
will be overwritten or overread.
SUBADDRESS DOUBLE BUFFERING MODE
The Enhanced Mini-ACE provides a double buffering mechanism
for received data, that may be selected on an individual subad-
dress basis for any or all receive (and/or broadcast) subad-
dresses. This is illustrated in FIGURE 7. It should be noted that
the Subaddress Double Buffering mode is applicable for receive
data only, not for transmit data. Double buffering of transmit
messages may be easily implemented by software techniques.
The purpose of the subaddress double buffering mode is to pro-
vide data sample consistency to the host processor. This is
accomplished by allocating two 32-word data word blocks for
each individual receive (and/or broadcast receive) subaddress.
At any given time, one of the blocks will be designated as the
"active "1553 block while the other will be considered as "inac-
tive". The data words for the next receive command to that sub-
address will be stored in the active block. Following receipt of a
valid message, the Enhanced Mini-ACE will automatically switch
the active and inactive blocks for that subaddress. As a result,
the latest, valid, complete data block is always accessible to the
host processor.
CIRCULAR BUFFER MODE
The operation of the Enhanced Mini-ACE's circular buffer RT
memory management mode is illustrated in FIGURE 8. As in the
single buffered and double buffered modes, the individual lookup
table entries are initially loaded by the host processor. At the
start of each message, the lookup table entry is stored in the
third position of the respective message block descriptor in the
descriptor stack area of RAM. Receive or transmit data words
are transferred to (from) the circular buffer, starting at the loca-
tion referenced by the lookup table pointer.
In general, the location after the last data word written or read
(modulo the circular buffer size) during the message is written to
the respective lookup table location during the end-of-message
sequence. By so doing, data for the next message for the respec-
tive transmit, receive(/broadcast), or broadcast subaddress will
be accessed from the next lower contiguous block of locations in
the circular buffer.
For the case of a receive (or broadcast receive) message with a
data word error, there is an option such that the lookup table
pointer will only be updated following receipt of a valid message.
That is, the pointer will not be updated following receipt of a
message with an error in a data word. This allows failed mes-
sages in a bulk data transfer to be retried without disrupting the
circular buffer data structure, and without intervention by the
RT's host processor.
24
FIGURE 6. RT SINGLE BUFFERED MODE
DATA
BLOCKS
DATA BLOCK
BLOCK STATUS WORD
TIME TAG WORD
DATA BLOCK POINTER
RECEIVED COMMAND
WORD
DESCRIPTOR
STACKS
LOOK-UP
TABLE ADDR
LOOK-UP TABLE
(DATA BLOCK ADDR)
15
13
0
CURRENT
AREA B/A
CONFIGURATION
REGISTER
STACK
POINTERS
(See note)
Note: Lookup table is not used for mode commands when enchanced mode codes are enabled.
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