HI-6121PQMF HOLTIC [Holt Integrated Circuits], HI-6121PQMF Datasheet - Page 78

• 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)
current pointer value. Similarly, Write command 0xC0
writes the location addressed by the current pointer value.
Two command bytes cannot be “chained”
negated after the Add command, then reasserted for the
following Read or Write command.
The primary address pointer is not affected by fast-access
read/writes to registers 0-14 because
commands use a separate, internal pointer not directly
accessible to the host.
Just two single-byte SPI commands use the current
address pointer value in register 15 without first loading or
otherwise modifying it:
Command
Command
Either of these commands can be used to read or write a
single location, or may be used when starting a multi-word
read or write by using the pointer’s auto-increment feature.
Two single-byte SPI commands increment the current
address pointer value in register 15, then perform a read or
write:
Command Read Operation
Command Write Operation
SCK
SPI Mode 0
SI
SO
CE
0xC0
0xC8
0x40
0x48
High Z
add 1 to pointer then write addressed location
add 1 to pointer then read addressed location
MSB
Read Operation
Write Operation
read location addressed by pointer value
write location addressed by pointer value
0
————————————
————————————
1
Command Byte
2
3
FIGURE 23. Single-Word (2-Byte) Write To RAM or a Register
4
5
6
fast-access SPI
LSB
7
HOLT INTEGRATED CIRCUITS
;
CE
MSB
0
must be
HI-6120, HI-6121
1
2
Data Byte 0
3
78
4
These two 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.
SPECIAL PURPOSE COMMANDS
Several other HI-6121 SPI commands load or otherwise
modify the primary address pointer before initiating a read
or write process. These commands were tailored to the
specific needs of HI-6121 Remote Terminal host software.
Using a single-byte SPI command, the address pointer can
be directly loaded with the memory address for the
descriptor table Control Word corresponding to the last
completed MIL-STD-1553 command. The Control Word is
then read.
Command Read Operation
This command can be used to read just the current Control
Word, or may be used to start a multi-word read because
memory pointer auto-increment occurs after the Control
Word is read.
Six single-byte SPI commands add an offset to the current
address pointer value, then read the addressed memory
location; the read value is then written to the address
pointer register 15. The new pointer value is used to start a
read or write operation:
5
0x50
6
LSB MSB
7
Copy Current Control Word Address register
13 to address pointer register 15. Read the
location addressed by the new pointer value.
0
————————————
————————————
1
2
Data Byte 1
3
4
Host may continue to assert
here to write sequential word(s).
Each word needs 16 SCK clocks.
5
6
LSB
7
CE