Technical information

5-6
AIC-6915 Ethernet LAN Controller Programmer’s Manual
Instruction Formats
Table 5-2 describes the Instruction Formats.
Table 5-2. Instruction Formats
Name Bit Number Description
Opcode 0 3:0
Execute
- Execute instruction as specified by control fields
Opcode 1 3:0
BrToImmIfTrue
- Branch to immediate address specified in
B
RANCH
A
DD
field if ALU flag is true
Opcode 2 3:0
BrToImmIfFalse
- Branch to immediate address specified in
B
RANCH
A
DD
field if ALU flag is false
Opcode 3 3:0
BrToWreg3IfTrue
- Branch to the location pointed to by WR3 if
ALU flag is True
Opcode 4 3:0
BrToWreg3IfFalse
- Branch to immediate address specified in
B
RANCH
A
DD
field if ALU flag is False
Opcode 5 3:0
Write
- Write ALU output to 8-bit address defined in
B
RANCH
A
DD
[7:0]
. If
B
RANCH
A
DD
[7]
is set the write operation is
targeted to a register implemented in the GFP module. If the bit is
reset the target register is implemented externally.
Opcode 6 3:0
Read
- Read location pointed to by the address defined in
B
RANCH
A
DD
[7:0]
, pass the data through the ALU and store it in
the working registers.
Opcode 7 3:0
Halt
- Halt the processor. Wait for the assertion of
ResetProcessor
input, then reset and start execution at address 0.
Opcode 8 3:0
CheckIpv4ProtocolId
- Special instruction for checking Ipv4
Protocol ID field, then branch to one of three possible addresses.
The GFP recognizes 3 Protocol IDs:
T
CP
F
RAME
I
D
= 8'h06, Branch address =
B
RANCH
A
DD
[7:0]
U
DP
F
RAME
I
D
= 8'h11, Branch address =
D
ATA
[7:0]
I
CMP
F
RAME
I
D
= 8'h00, Branch address =
D
ATA
[15:8
]
Opcode 9 3:0
ReadIpv6ExtHeader
- Special instruction for reading the Next
Header and Length fields of an Ipv6 extension header. After the
instruction is executed, WR2 stores the size of the extension header
in 16-bit halfword units minus 1 (for the first 16-bit already read).
WR3 stores the total size of the frame in bytes. WR4 stores the Next
Header field.