Inputs | Outputs | Parameters

decoder Module Reference

Decode instruction and addressing mode. More...

Inheritance diagram for decoder:
ao68000

List of all members.

Inputs

clock  
reset_n  
supervisor  
ir  [15:0]
ea_type  [3:0]
ea_mod  [2:0]
ea_reg  [2:0]

Outputs

decoder_trap  [7:0]
decoder_micropc  [8:0]
decoder_alu  [17:0]
save_ea  [8:0]
perform_ea_write  [8:0]
perform_ea_read  [8:0]
load_ea  [8:0]

Parameters

NO_TRAP  [7:0] 8'd0
ILLEGAL_INSTRUCTION_TRAP  8'd4
PRIVILEGE_VIOLATION_TRAP  8'd8
ILLEGAL_1010_INSTRUCTION_TRAP  8'd10
ILLEGAL_1111_INSTRUCTION_TRAP  8'd11
UNUSED_MICROPC  [8:0] 9'd0

Detailed Description

Decode instruction and addressing mode.

The decoder is an instruction and addressing mode decoder. For instructions it takes as input the ir register from the registers module. The output of the decoder, in this case, is a microcode address of the first microcode word that performs the instruction.

In case of addressing mode decoding, the output is the address of the first microcode word that performs the operand loading or saving. This address is obtained from the currently selected addressing mode saved in the ea_mod and ea_type registers in the registers module.

Definition at line 2159 of file ao68000.v.


Member Data Documentation

clock [Input]

Definition at line 2160 of file ao68000.v.

reset_n [Input]

Definition at line 2161 of file ao68000.v.

supervisor [Input]

Definition at line 2163 of file ao68000.v.

ir [15:0] [Input]

Definition at line 2164 of file ao68000.v.

decoder_trap [7:0] [Output]

Definition at line 2167 of file ao68000.v.

decoder_micropc [8:0] [Output]

Definition at line 2168 of file ao68000.v.

decoder_alu [17:0] [Output]

Definition at line 2169 of file ao68000.v.

save_ea [8:0] [Output]

Definition at line 2171 of file ao68000.v.

perform_ea_write [8:0] [Output]

Definition at line 2172 of file ao68000.v.

perform_ea_read [8:0] [Output]

Definition at line 2173 of file ao68000.v.

load_ea [8:0] [Output]

Definition at line 2174 of file ao68000.v.

ea_type [3:0] [Input]

Definition at line 2176 of file ao68000.v.

ea_mod [2:0] [Input]

Definition at line 2177 of file ao68000.v.

ea_reg [2:0] [Input]

Definition at line 2178 of file ao68000.v.

NO_TRAP [7:0] 8'd0 [Parameter]

Definition at line 2181 of file ao68000.v.

ILLEGAL_INSTRUCTION_TRAP 8'd4 [Parameter]

Definition at line 2181 of file ao68000.v.

PRIVILEGE_VIOLATION_TRAP 8'd8 [Parameter]

Definition at line 2181 of file ao68000.v.

ILLEGAL_1010_INSTRUCTION_TRAP 8'd10 [Parameter]

Definition at line 2181 of file ao68000.v.

ILLEGAL_1111_INSTRUCTION_TRAP 8'd11 [Parameter]

Definition at line 2181 of file ao68000.v.

UNUSED_MICROPC [8:0] 9'd0 [Parameter]

Definition at line 2188 of file ao68000.v.


The documentation for this class was generated from the following file: