
GR716-DS-UM, May 2019, Version 1.29
452
www.cobham.com/gaisler
GR716
Dedicated registers for write address and read address is implemented, these registers takes value
from this command. The purpose of this register is to access up to 32 bits of address space. The most
significant word CW1 (or CR1) contains the most significant bytes of the target address.
Redundancy commands
The SPI Slave device has two dedicated interfaces for two masters. The masters can send to its corre-
sponding slave interface to activate or deactivate the other SPI interface. The master device cannot
activate or deactivate the same ports on which it is connected, it can only activate or deactivate the
other ports.
Initially both the SPI port interfaces are enabled to receive commands, when the communication
between the nominal master and slave interface fails then the redundant master can deactivate the
nominal interface using its dedicated redundant interface. The redundant master can also activate the
nominal interface.
An example switchover scenario from nominal to redundant interface is described in the following
text.
The nominal master communicates with its dedicated interface to a slave device, a fault occurred can
be detected by the master using several options,
The status received by the master have invalid values (using the response token),
The Read back command sent does not provide appropriate values in the received payload,
Error bits are enabled in the status received by the master (using the response token),
Based on any of the above mentioned fault detection methods the master can send deactivate com-
mand in the redundant interface to deactivate the nominal interface of the slave. The master can send
Read back sent commands (using redundant) to check if the previous deactivate command was
received by the slave and can check the status of the response token as well. After conforming a
proper communication has been established the master can use the redundant interface to perform its
normal operations.
Any other commands which are not implemented is received then the command token is discarded
and Status illegal command (SIC) bit is enabled and also transmitted to master as part of the next
response token.
Table 605.
Redundancy commands
Code
Command
Length
Sub-
Address
Payload
Description
0x24
ACTIVATE
0x00
0x00
None
The command is used to activate the other
slave interface. This command cannot acti-
vate the interface in which it is receiving
this command.
0x25
DEACTIVATE
0x00
0x00
None
The command is used to deactivate the other
slave interface. This command cannot deac-
tivate the interface in which it is receiving
this command.