User`s manual

Software Manual • EKF Intelligent I/O Controller Family On CompactPCI
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Command Word Structure
Commands passed to the controller via the Inbound Message Register IMR0 are called
messages. A message consists of a command word and belonging parameters or data. The
command word contains the meaning of the message, the device number involved with the
message, the size of belonging parameters or data and some flags. The next figure shows
the general layout of the command word, 32 bit in size:
General Command Word Format
Flags Port ID Command Command Data
E
R
R
R
P
L
C
P
L
U
F
ID
3
ID
2
ID
1
ID
0
C
7
C
6
C
5
C
4
C
3
C
2
C
1
C
0
D
15
D
14
D
13
D
12
D
11
D
10
D
09
D
08
D
07
D
06
D
05
D
04
D
03
D
02
D
01
D0
0
31 28 27 24 23 16 15 8 7 0
ERR Error Flag Set by the controller to indicate an error condition. The command data
field contains a 16 bit error code when ERR is set.
RPL Reply Flag Set by the controller when replying to a command.
CPL Complete Flag Set by the controller to indicate that a command was completed.
UF Unused Flag For compatibility this flag should be passed to the controller always as 0. It
is currently never touched by the controller.
ID3:0 Port Identifier A zero base ID used to specify 1 of 16 devices (e.g. UARTs).
C7:0 Command Code The command code defining the meaning of the message (e.g.
WRITE_DATA).
D15:00 Command Data The contents of this field is dependent of the command code of the
message. For example it could contain the size of the data belonging to
the message or it could be a parameter itself.
The command word is defined as a union of type EKF_IMR_COMMAND in the C header
“ekf960if.h”.