HI-6121PQMF HOLTIC [Holt Integrated Circuits], HI-6121PQMF Datasheet - Page 45

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

DESCRIPTOR TABLE, Cont.
7-4
3
2
1-0
MESSAGE DATA BUFFERS
The memory structures described up to this point comprise
not more than 1K words of the lower memory address
space. The remaining memory is allocated by the host for
message data storage, to fulfill application requirements.
This section describes the remaining data structures in
shared RAM that control (and result from) command
processing.
By initializing the Descriptor Table, the host allocates
memory space for storing data for each subaddress used
in the Remote Terminal application. Each legal Receive
Subaddress and each legal Transmit Subaddress are
usually assigned unique buffer memory spaces.
(Exception: To comply with the requirements for MIL-STD-
1553 data wrap-around, it is convenient to assign the data
wrap-around subaddress to use the same buffer space for
both receive and transmit commands.)
As an option, data from broadcast receive commands can
be stored separately from data resulting from non-
broadcast receive commands. Each subaddress buffer
can use any of four data storage methods offered.
Subaddress (non-mode) commands are transacted with
one to 32 data words. These are stored in a data buffer in
——
STOPP
PPEN
——
Not used.
Stop Ping-Pong Request.
The host asserts this bit to suspend ping-pong buffering for this mode code. The host resets this bit to
ask the device to re-enable ping-pong. The device confirms recognition of ping-pong enable or
disable status by writing PPON bit 3.
Ping-Pong Buffer Enable.
The PPEN bit is initialized by the host to select buffer mode. If this bit is high, ping-pong buffering is
selected. If this bit is low, indexed single buffering is selected.
After reset, the host initializes this bit to logic 1 to enable ping-pong buffering for this mode code. The
host asserts STOPP bit 3 to ask the device to temporarily disable ping-pong. Negating the STOPP bit
asks the device to re-enable ping-pong. The device confirms ping-pong enable or disable state
changes by writing the PPON bit.
Not used.
HOLT INTEGRATED CIRCUITS
HI-6120, HI-6121
45
shared RAM. For receive commands, the device stores
data received during message processing in the shared
RAM buffer. Later, the host retrieves these data words from
the buffer. In the case of transmit commands, the host has
previously stored transmit data words in the transmit
subaddress buffer. The device retrieves these data words
for transmission while processing the transmit command.
For each complete message processed, the
data stored in the buffer is comprised of these elements:
The Message Information word and Time-Tag word are
generated by the device and stored in assigned buffer
space to aid the host in further message processing. The
Message Information word contains message type, word
count and message error information. The 16-bit Time-Tag
word contains the value in the device internal Time-Tag
counter when the command is validated.
1. Message Information Word
2. Time-Tag Word
3. One to 32 Data Words transmitted or received
during message transaction ( except no data
word for mode code commands 0 - 15 decimal)
message