Basic operating system...

4 files changed, 108 insertions, 8 deletions

diff --git a/asm/asmlex.mll b/asm/asmlex.mll
index 7be493e..7459966 100644
--- a/asm/asmlex.mll
+++ b/asm/asmlex.mll
@@ -94,6 +94,10 @@ rule token = parse
 					with Not_found -> ID id }
 	| "0x" (((hexdigit)+) as n)
 		{ INT (read_16 n) }
+    | "'\\n'" { INT (Char.code '\n') }
+    | "'\\t'" { INT (Char.code '\t') }
+    | "'\\r'" { INT (Char.code '\r') }
+    | "'" (_ as c) "'" { INT (Char.code c) }
 	| (digit)+ as n { INT (int_of_string n) }
 	| "0b" (['0' '1']+ as n) { INT (read_2 n) }
 	| ['A'-'Z']+ as name { try REG (List.assoc name regs) with Not_found -> raise (Asm_error ("no reg " ^ name))}
diff --git a/asm/assembler.ml b/asm/assembler.ml
index 66999fb..8c8ff97 100644
--- a/asm/assembler.ml
+++ b/asm/assembler.ml
@@ -2,6 +2,8 @@ open Asm
 open Printf
 open Lexing
 
+exception No_such_label of string
+
 let init_string n f =
 	let res = String.make n 'a' in
 	for i = 0 to n - 1 do res.[i] <- f i done; res
@@ -83,13 +85,13 @@ let print_program p =
 	let pc = ref 0 in
 	let value = function
 		| Imm i -> i
-		| Lab l -> fst (Imap.find l p.lbls) in
+		| Lab l -> try fst (Imap.find l p.lbls) with Not_found -> raise (No_such_label l) in
 	let value2 = function
 		| Imm i -> i
-		| Lab l -> fst (Imap.find l p.lbls) - !pc in
+		| Lab l -> try fst (Imap.find l p.lbls) - !pc with Not_found -> raise (No_such_label l) in
 	let value3 = function
 		| Imm i -> i
-		| Lab l -> (byte 16 (fst (Imap.find l p.lbls))) lsr 8 in
+		| Lab l -> try (byte 16 (fst (Imap.find l p.lbls))) lsr 8 with Not_found -> raise (No_such_label l) in
 	let get_reps = function
 		| R (o,r1,r2,r3) -> r (code o) r1 r2 r3,
 			sprintf "%s %s %s %s" (List.assoc o rev_keywords) (rts r1) (rts r2) (rts r3)
diff --git a/cpu/cpu.ml b/cpu/cpu.ml
index 1d1eea8..3f9dd74 100644
--- a/cpu/cpu.ml
+++ b/cpu/cpu.ml
@@ -56,6 +56,7 @@ let cpu_ram ra we wa d =
     let iser = nonnull 8 ser_in in
     let ser = mux iser ser ser_in in
     let ser_busy = nonnull 8 ser in
+    let ser_busy = mux read_ser ser_busy (const "0") in
     let read_data =
         save_ser_in_busy ser_busy ^.
         save_next_ser (mux read_ser ser (zeroes 8)) ^.
diff --git a/cpu/os.asm b/cpu/os.asm
index 5d58ff7..4a7449a 100644
--- a/cpu/os.asm
+++ b/cpu/os.asm
@@ -1,15 +1,58 @@
+# CONVENTION:
+#       return value for functions : in register A
+#       arguments for functions : registers A, B, C, D
+#       all registers are caller-saved, except SP which is preserved by function calls
+
 .text
-init:
+    li A msghello
+    jal ser_out_msg
+
+    push Z
+main_loop:
+    # Process serial input
+    jal check_input
+    jz A end_process_input
+    jal run_cmd
+end_process_input:
+
+    # Process clock ticking
+    pop D
     li B _clock
     lw B 0(B)
-    jz B init
     add D D B
     push D
+
+    jz B main_loop
     li A msgtick
     jal ser_out_msg
-    pop D
-    j init
+    j main_loop
+
+# PROCEDURE: run_cmd
+# ROLE: execute and clear command stored in cmdline
+# ARGUMENTS: none
+run_cmd:
+    push RA
+
+    li A prompt
+    jal ser_out_msg
+    li A cmdline
+    jal ser_out_msg
+    li A endl
+    jal ser_out_msg
+    
+    li A error
+    jal ser_out_msg
 
+    li A cmdline_used
+    sw Z 0(A)
+
+    pop RA
+    jr RA
+    
+
+# PROCEDURE: ser_out_msg
+# ROLE: write null-terminated string to serial output
+# ARGUMENTS: address of string in register A
 ser_out_msg:
     li C _output
 ser_out_msg_loop:
@@ -21,5 +64,55 @@ ser_out_msg_loop:
 ser_out_msg_ret:
     jr RA
 
+# PROCEDURE: check_input
+# ROLE: check if an input byte is available. if it is, and is different from '\n' (10), add it to cmdline
+# ARGUMENTS: none
+# RETURN VALUE: 1 if read byte was '\n', 0 otherwise
+# WARNING: no buffer overflow check.
+check_input:
+    li A _input
+    lb A 0(A)
+    jz A check_input_ret
+    move B A
+    sei A A '\n'
+    jz A add_b_to_string
+    move B Z
+add_b_to_string:
+    push A
+    li A cmdline
+    li D cmdline_used
+    lw C 0(D)
+    add A A C
+    sb B 0(A)
+    incri C 1
+    sw C 0(D)
+    pop A
+check_input_ret:
+    jr RA
+    
+
+# READ-ONLY PROGRAM DATA
+msghello:
+    ascii "Hello, world!\n"
 msgtick:
-    ascii "Tick!"
+    ascii " ..."
+prompt:
+    ascii "\n$ "
+endl:
+    ascii "\n"
+error:
+    ascii "Sorry but I'm to stupid to understand that.\n"
+
+
+.data
+# Space where command-line is buffered from serial input
+cmdline:
+    byte 256
+# Number of bytes used in the command-line buffer
+cmdline_used:
+    word 1
+
+
+
+
+