HI-6121PQMF HOLTIC [Holt Integrated Circuits], HI-6121PQMF Datasheet - Page 54

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

PING-PONG DATA BUFFERING, Cont.
to acknowledge ping-pong is disabled. While PPON
remains low, the last written (or read) data buffer is
protected against device updates. During this time, new
messages use the active buffer indicated by the
Word DPA bit. R
same buffer until ping-pong resumes.
(b) Host services the last-used data buffer. If the Control
Word DPB bit equals logic 1, the last command used Buffer
A. The host application software off-loads or loads inactive
Buffer A while the remote terminal uses active Buffer B for
new message(s). If the DPB bit equals logic 0, the last
command used Buffer B. The host application software off-
loads or loads inactive Buffer B while the remote terminal
uses active Buffer A for any new messages.
receive message overwrites buffer contents from the last
receive message. To avoid possible data loss, host buffer
servicing should be timed for completion before a second
message can occur.
(c) Host negates the Control Word STOPP bit to resume
ping-pong operation for the subaddress. When the RT
recognizes the STOPP bit is reset, it sets the PPON bit to
acknowledge ping-pong is again active. As long as PPON
remains set, the device alternates between data buffers A
and B for new messages.
BROADCAST MESSAGE HANDLING
IN PING-PONG MODE
For MIL-STD-1553B Notice II compliance, a remote
terminal should be capable of storing data from broadcast
messages separately from non-broadcast message data.
Some applications may not include this requirement. The
standard does not stipulate where data separation should
occur (e.g., within the RT or within the external host) so the
device provides alternative strategies.
When the NOTICE2 bit in Configuration Register 1 is 1 and
the BCSTINV bit is 0, ping-pong mode subaddresses (or
mode codes) will buffer data words from broadcast and
non-broadcast messages separately. Broadcast message
information and data are stored in the broadcast data
buffer; non-broadcast message information and data are
stored in ping-pong buffers A and B. Since there is just one
broadcast data buffer, the NOTICE2 option treats
broadcast messages as exceptions to normal ping-pong
mode. When using the NOTICE2 option, broadcast data
buffer servicing should have high priority, because a
closely following broadcast message will overwrite the
broadcast buffer.
Every mode command and subaddress (including
transmit subaddresses) must have an assigned valid
broadcast data pointer when NOTICE2 is asserted
When the NOTICE2 bit in Configuration Register 1 is 1 and
the BCSTINV bit is 0, r
message updates the Message Information and Time-Tag
Words for the assigned broadcast buffer, but no data is
transmitted on the bus. Since broadcast-transmit is not
allowed, multiple transmit subaddresses may share a
ecurring messages repeatedly use the
eception of a broadcast-transmit
HOLT INTEGRATED CIRCUITS
Each new
Control
HI-6120, HI-6121
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common “bit bucket” broadcast buffer. A two word buffer is
sufficient for storing the MIW and Time-Tag Word.
When using ping-pong mode, there are two ways to handle
broadcast messages, when broadcast is enabled:
Option 1 for Ping-Pong Mode Broadcast Messages:
This option isolates broadcast message information in the
broadcast data buffer. If the descriptor Control Word IBRD
bit and Interrupt Enable Register IBRD bit are both set,
reception of broadcast messages generates an
host interrupt. To prevent data loss, the broadcast data
buffer must be serviced before the next broadcast
message occurs. Broadcast messages do not affect non-
broadcast message ping-pong; the Control Word DPB bit
does not toggle after broadcast message completion.
Option 1 Setup:
NOTICE2 bit in Configuration Register 1 and sets the IBRD
(Interrupt Broadcast Received) bit in descriptor Control
Word(s). The IBRD bit is asserted in the Interrupt Enable
Register.
When a broadcast command is received, message
information and data is stored in the broadcast data buffer
and an
the Interrupt Log to determine the originating subaddress
(or mode code), then service the broadcast data buffer for
that subaddress (or mode code) before another broadcast
message to the same subaddress (or mode code) arrives.
Option 2 for Ping-Pong Mode Broadcast Messages:
The second alternative stores both broadcast and non-
broadcast message information in the ping-pong data
buffers A and B. IWA interrupts can signal arrival of any
new message. The RT handles broadcast messages just
like non-broadcast messages, except the Message
Information Word BCAST bit is asserted to identify
broadcast messages during host buffer servicing. All
messages toggle the Control Word DPB bit in message
post-processing. For Notice II compliance, separation of
broadcast and non-broadcast data occurs within the host.
Option 2 Setup:
NOTICE2 bit in Configuration Register 1. If IWA interrupts
are used, the host asserts the descriptor Control Word IWA
(Interrupt When Accessed) bit 14 and the corresponding
bit is asserted in the Interrupt Enable Register. Using this
option, the IBRD interrupt is probably not used.
The host typically services the ping-pong data buffers A
and B whenever a message is transacted. Using the setup
above, this occurs whenever the subaddress IWA interrupt
generates an
host must read the Interrupt Log to determine the
originating subaddress or mode code. The applicable data
buffer is indicated by the DPB bit in the Receive Control
Word. The Message Information Word BCAST bit is
asserted if the message was broadcast.
INTMES
INTMES
interrupt is generated. The host must read
At initialization, host negates the
At initialization, host asserts the
interrupt output for the host. The
INTMES