HI-6121PQMF HOLTIC [Holt Integrated Circuits], HI-6121PQMF Datasheet - Page 35

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

DESCRIPTOR TABLE
The Descriptor Table, resides in shared RAM, in address
range 0x0200 to 0x03FF. This table is initialized by the host
(or auto-initialization) to define how the terminal processes
valid commands. Descriptor Table settings for each
command specify where message data is stored, how data
is stored, whether host interrupts are generated, and other
aspects essential to command processing. Shown in
Figure 9, the table consists of 128 consecutive “descriptor
blocks”, each comprised of four 16-bit words. The table is
organized into four quadrants.
The Receive Subaddress and Transmit Subaddress
quadrants define response for commands having a
subaddress field ranging from 1 to 30 (0x1E). These are
simple N-data word receive or transmit commands, where
N can range from 1 to 32 words. When the command T/R
bit equals 0, the receive command quadrant applies. When
the
applies.
Both subaddress quadrants are padded at top and bottom
with unused Descriptor Blocks for subaddresses 0 and 31
(0x1F). The word space reserved for SA0 and SA31 aligns
the table addressing, but values stored in these eight
locations is not used. Command subaddresses 0 and 31
indicate mode commands. The response for commands
containing either SA value is defined in the two mode
command table quadrants. The Receive Mode Command
quadrant applies when the command word
0, while the Transmit Mode Command quadrants applies
when
The term “Transmit Mode Command” is a misnomer. All
defined mode commands with mode code less than 0x0F
have
transmits a data word. They transmit only the terminal
status word, just like receive commands.
Within the Receive and Transmit Mode Command
quadrants, block addressing is based on the low order 5
bits in the command word, containing the mode code
value. This is fundamentally different from the Subaddress
quadrants in which block addressing is based on the 5-bit
subaddress field. Figure 10 shows how to derive Control
Word address from the received Command Word. The
Control Word address for the last valid command can also
be found in the Current Control Word Address register.
All 128 4-word Descriptor Blocks start with a Control Word.
There are four Control Word variants, based on command
type: receive vs. transmit and mode vs. non-mode
commands. The four Control Word types are defined
beginning with the next page.
All descriptor Control Words are initialized by the host (or
auto-initialization) to define basic command response.
T/
T/
T/
R
R
R
bit equals 1, the transmit command quadrant
bit equal to 1, yet none of these mode commands
equals 1.
HOLT INTEGRATED CIRCUITS
T/
R
bit equals
HI-6120, HI-6121
35
Each Control Word specifies the data buffer method and
host interrupt for a specific subaddress or mode command.
Each subaddress has both a Receive Subaddress block
and a Transmit Subaddress block. Receive and transmit
commands to the same subaddress can be programmed
to respond differently.
The function of the three remaining descriptor words (in
each 4-word block) depends on the data buffer method
specified in the Control Word. Function of descriptor words
2 through 4 is explained within later data sheet sections for
the four available data buffer options, briefly listed here:
Indexed (or Single Buffer) Method
predetermined number of messages is transacted using a
single data buffer in shared RAM. Several host interrupt
options are offered, including an interrupt generated when
all N messages are successfully completed.
Double (or Ping-Pong) Buffer Method
messages alternate between two data buffers in shared
RAM. Several host interrupt options are offered.
Circular Buffer Mode 1
determine when the bulk transfer is complete and
message information and time-tag words are stored with
message data in a common buffer. Several host interrupt
options are offered, including an interrupt generated when
the allocated data buffer is full.
Circular Buffer Mode 2
transacted defines bulk transfer progress, and message
data words are stored contiguously in one buffer while
message information and time-tag words are stored in a
separate buffer. Several host interrupt options are offered,
including an interrupt generated when all N messages are
successfully completed.
The 4-word Descriptor Table entry for each command (its
descriptor block) begins with a Control Word. There are
four types of descriptor Control Word:
The descriptor Control Word is initialized by the host to
select data buffer method and interrupt options.
command is processed by the HI-6120 terminal, the device
updates the command’s descriptor Control Word. Update
will differ based on the chosen data buffer method.
The four descriptor Control Word types are explained next.
Receive Subaddress Control Word
Transmit Subaddress Control Word
Receive Mode Command Control Word
Transmit Mode Command Control Word
where the number of messages
where buffer boundaries
where successive
where a
After a