From adb1aa800d0071a1bccf122c2d48e9fa278f19a0 Mon Sep 17 00:00:00 2001
From: Alex AUVOLAT <alex.auvolat@ens.fr>
Date: Tue, 14 Jan 2014 15:17:34 +0100
Subject: Implement basic clock.

---
 cpu/os.asm | 231 +++++++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 201 insertions(+), 30 deletions(-)

diff --git a/cpu/os.asm b/cpu/os.asm
index 72598c6..9a3d7a6 100644
--- a/cpu/os.asm
+++ b/cpu/os.asm
@@ -12,9 +12,18 @@
     jal run_unit_tests 
 
     li A msghello
-    jal ser_out_msg
+    jal ser_out_str
+
+    li A 1994
+    li B var_year
+    sw A 0(B)
+    li A 2
+    li B var_month
+    sb A 0(B)
+    li A 26
+    li B var_day
+    sb A 0(B)
 
-    push Z
 _main_loop:
     # Process serial input
     jal check_input
@@ -23,17 +32,118 @@ _main_loop:
 _end_process_input:
 
     # Process clock ticking
-    pop D
     li B _clock
-    lw B 0(B)
-    add D D B
-    push D
+    lw A 0(B)
+    jz A _main_loop
 
-    jz B _main_loop
-    li A msgtick
-    jal ser_out_msg
+    jal incr_clock
+    jal disp_time
     j _main_loop
 
+# PROCEDURE: incr_clock
+# ROLE: take into account seconds increment
+# ARGUMENTS: number of seconds to add, in register A
+incr_clock:
+    jz A _incr_clock_ret
+
+    lb B var_sec
+    add B B A
+    li C 60
+    divu A B C
+    move B E
+    sb B var_sec
+    jz A _incr_clock_ret
+
+    lb B var_min
+    add B B A
+    divu A B C
+    move B E
+    sb B var_min
+    jz A _incr_clock_ret
+
+    lb B var_hour
+    add B B A
+    li C 24
+    divu A B C
+    move B E
+    sb B var_hour
+    jz A _incr_clock_ret
+
+    lb B var_day
+    add B B A
+    lb C var_month
+    li D days_in_month
+    add D D C
+    lb C 0(D)
+    divu A B C
+    move B E
+    sb B var_day
+    jz A _incr_clock_ret
+
+    lb B var_month
+    add B B A
+    li C 12
+    divu A B C
+    move B E
+    sb B var_month
+    jz A _incr_clock_ret
+
+    lw B var_year
+    add B B A
+    sw B var_year
+
+
+_incr_clock_ret:
+    jr RA
+
+# PROCEDURE: disp_clock
+# ROLE: display current time
+# ARGUMENTS: none
+disp_time:
+    push RA
+
+    lw A var_year
+    jal ser_out_int_dec
+    li A '-'
+    li E _output
+    sb A 0(E)
+    
+    lb A var_month
+    incri A 1
+    jal ser_out_int_dec_two_digit
+    li A '-'
+    li E _output
+    sb A 0(E)
+
+    lb A var_day
+    incri A 1
+    jal ser_out_int_dec_two_digit
+    li A ' '
+    li E _output
+    sb A 0(E)
+
+    lb A var_hour
+    jal ser_out_int_dec_two_digit
+    li A ':'
+    li E _output
+    sb A 0(E)
+
+    lb A var_min
+    jal ser_out_int_dec_two_digit
+    li A ':'
+    li E _output
+    sb A 0(E)
+     
+    lb A var_sec
+    jal ser_out_int_dec_two_digit
+    li A '\n'
+    li E _output
+    sb A 0(E)
+
+    pop RA
+    jr RA
+
+
 # PROCEDURE: run_cmd
 # ROLE: execute and clear command stored in cmdline
 # ARGUMENTS: none
@@ -41,14 +151,14 @@ run_cmd:
     push RA
 
     li A prompt
-    jal ser_out_msg
+    jal ser_out_str
     li A cmdline
-    jal ser_out_msg
+    jal ser_out_str
     li A endl
-    jal ser_out_msg
+    jal ser_out_str
     
     li A error
-    jal ser_out_msg
+    jal ser_out_str
 
     li A cmdline_used
     sw Z 0(A)
@@ -57,18 +167,63 @@ run_cmd:
     jr RA
     
 
-# PROCEDURE: ser_out_msg
+# PROCEDURE: ser_out_int_dec
+# ROLE: write a decimal integer to serial output
+# ARGUMENTS: integer to write in register A
+ser_out_int_dec:
+    jz A _display_zero
+    push Z
+    li B 10
+_divide_int_by_ten:
+    jz A _show_dec
+    divu A A B
+    move C E
+    addi C C '0'
+    push C
+    j _divide_int_by_ten
+_show_dec:
+    li C _output
+    pop A
+    jz A _return_out_dec
+    sb A 0(C)
+    j _show_dec
+_return_out_dec:
+    jr RA
+_display_zero:
+    li C _output
+    li D '0'
+    sb D 0(C)
+    jr RA
+
+# PROCEDURE: ser_out_two_digit
+# ROLE: write only the two lower digits of a decimal integer to serial output
+# ARGUMENTS: integer to write in register A
+ser_out_int_dec_two_digit:
+    li B 10
+    divu A A B
+    move C E
+    divu A A B
+    move D E
+    li B _output
+    addi D D '0'
+    addi C C '0'
+    sw D 0(B)
+    sw C 0(B)
+    jr RA
+
+
+# PROCEDURE: ser_out_str
 # ROLE: write null-terminated string to serial output
 # ARGUMENTS: address of string in register A
-ser_out_msg:
+ser_out_str:
     li C _output
-_ser_out_msg_loop:
+_ser_out_str_loop:
     lb B 0(A)
-    jz B _ser_out_msg_ret
+    jz B _ser_out_str_ret
     sb B 0(C)
     incri A 1
-    j _ser_out_msg_loop
-_ser_out_msg_ret:
+    j _ser_out_str_loop
+_ser_out_str_ret:
     jr RA
 
 # PROCEDURE: check_input
@@ -105,7 +260,7 @@ run_unit_tests:
     push RA
 
     li A testbegin
-    jal ser_out_msg
+    jal ser_out_str
 
     move B Z
 
@@ -120,14 +275,14 @@ _unit_test_begin:
     li A teststr
     add A A B
     lw A 0(A)
-    jal ser_out_msg
+    jal ser_out_str
     pop D
     jalr D
     li A testfail
     jz B _unit_test_failed
     li A testok
 _unit_test_failed:
-    jal ser_out_msg
+    jal ser_out_str
 
     pop B
     addi B B 2
@@ -198,14 +353,14 @@ unit_test_2:        # Unsigned division
     sei A D 1
     and B B A
 
-    #li C 61
-    #li D 5
-    #divu C C D
-    #move D E
-    #sei A C 12
-    #and B B A
-    #sei A D 1
-    #and B B A
+    li C 54200
+    li D 4203
+    divu C C D
+    move D E
+    sei A C 12
+    and B B A
+    sei A D 3764
+    and B B A
 
     jr RA
 unit_test_3:        # Signed multiplication/division
@@ -228,6 +383,7 @@ endl:
 error:
     ascii "Sorry but I'm to stupid to understand that.\n"
 
+
 # For unit-tests
 testlist:
     word unit_test_0 unit_test_1 unit_test_2 unit_test_3 0
@@ -249,6 +405,9 @@ test3:
     ascii "Signed multiplication/division. "
 
 
+days_in_month:
+    byte 31 28 31 30 31 30 31 31 30 31 30 31
+
 
 .data
 # Space where command-line is buffered from serial input (256 bytes)
@@ -258,6 +417,18 @@ cmdline:
 cmdline_used:
     word 1
 
+var_sec:
+    byte 1
+var_min:
+    byte 1
+var_hour:
+    byte 1
+var_day:
+    byte 1
+var_month:
+    byte 1
+var_year:
+    word 1
 
 
 
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