HI-6121PQMF HOLTIC [Holt Integrated Circuits], HI-6121PQMF Datasheet - Page 79

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

HOST SERIAL PERIPHERAL INTERFACE, Cont. (HI-6121 ONLY)
Command Read Operation
Command Write Operation
Primary use occurs when a Descriptor Table Control Word
was just read. For example, the last op code performed
was 0x50, reading the Control Word for the last command.
After reading the Control Word, the memory pointer has
automatically incremented. The host can examine flag bits
contained in the just-read Control Word to determine the
applicable data buffer (e.g., Data Buffer A, Data Buffer B or
the Broadcast Data Buffer) then directly service that buffer
using these op codes; the three data buffer pointers occur
in the three words following the initially read Control Word.
These six commands can be used to read or write a single
location, or may be used to start a multi-word read or write
that uses the pointer’s auto-increment feature.
When some or all subaddress or mode commands are not
programmed to trigger host interrupts, a different single-
byte SPI command may be useful if polling the Descriptor
Table for message activity. In this situation, the host may
poll a series of Descriptor Table Control Words looking for
instances where the DBAC activity bit is set. The DBAC
(Descriptor Block Accessed) flag is set in the Control Word
each time the corresponding command is completed. The
process of reading the Control Word automatically resets
the register’s DBAC bit so the host can detect activity the
next time the DBAC flag is set by the device.
Since Descriptor Table Control Words are spaced four
words apart, this command is useful when polling a series
of descriptor table Control Words:
0xE8
0xF0
0xF8
0x68
0x70
0x78
Read the location addressed by the memory
address pointer. Write the value just read into
the memory address pointer. Then read.
Add 1 to the memory address pointer. Read
value at newly addressed location and write it
into the memory address pointer. Then read.
Add 2 to the memory address pointer. Read
value at newly addressed location and write it
into the memory address pointer. Then read.
Read the location addressed by the memory
address pointer. Write the value just read into
the memory address pointer. Then write.
Add 1 to the memory address pointer. Read
value at newly addressed location and write it
into the memory address pointer. Then write.
Add 2 to the memory address pointer. Read
value at newly addressed location and write it
into the memory address pointer. Then write.
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HOLT INTEGRATED CIRCUITS
HI-6120, HI-6121
79
Command Read Operation
Primary use occurs when the address pointer initially
points to the first Descriptor Table Control Word in a series
of Control Words to be polled (every fourth word).
After 8 SCK clocks for the SPI command, each instance of
this command reads a single location using 16 SCK clocks.
If
multi-word read begins, using the address pointer’s auto-
increment feature. The second word read is at (Control
Word address + 4), the next Control Word in the table.
Another single-byte SPI command is useful when
servicing interrupts. When enabled interrupts occur, two
words are written to the circular 32-word Interrupt Log
Buffer, and the Interrupt Log Address register 9 is updated
to show the storage address where interrupt information
words will be stored
Buffer starting address is 0x0040 and ending address is
0x005F. Because two words are written to the buffer for
each interrupt, the Interrupt Log Address register always
contains an even value in the range of 0x0040 to 0x005E.
When servicing an interrupt that just occurred, the host
wants timely information on that interrupt. An SPI
command is provided to simplify interrupt handling:
Command Read Operation
This command can be used to read a single location, or
may be used to start a multi-word read in which the
memory address pointer automatically decrements after
each word read. This is the only SPI op code that
decrements the memory pointer for multi-word operations.
Repeated memory pointer decrements will wrap around
the 0x0040 to 0x005F log buffer boundary.
CS
0x60
0x58
remains low after 24 clocks and SCK continues, a
write memory address pointer 0x000F with
current value in Interrupt Log Address register
minus 1. If the Log Address register contains
0x0040 then 0x005F is written to memory
pointer register. Then read the addressed
RAM location, containing the last-written
Interrupt Address Word. Then decrement the
memory address pointer, addressing the
corresponding Interrupt Information Word.
read addressed location then add 4 to pointer
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for the next occurring interrupt
.