Allow reactivating crossing during deactivation sequence

1 files changed, 42 insertions, 4 deletions

diff --git a/assembly/rrxing2/rrxing2.S b/assembly/rrxing2/rrxing2.S
index f9308f8..ba8dac9 100644
--- a/assembly/rrxing2/rrxing2.S
+++ b/assembly/rrxing2/rrxing2.S
@@ -110,9 +110,11 @@ addi t1,t1,1 # And add 1 to get to the first non-idle state
 la t0,currstate
 sb t1,0(t0) # Update state in RAM to the first state in the current country
 la t0,states
-sh2add t0,t1,t0 # Calculate the proper offset in the list of pointers (state number * 4 + base address)
-lw t0,0(t0) # Load the pointer
-jalr ra,t0,0 # And call that function
+addi t2,t1,1 # Landing pad label is state number + 1 (to avoid having any of them be 0)
+slli t2,t2,12
+sh2add t1,t1,t0 # Calculate the proper offset in the list of pointers (state number * 4 + base address)
+lw t1,0(t1) # Load the pointer
+jalr ra,t1,0 # And call that function
 
 2: la t0,currstate
 lb s0,0(t0) # Re-read current state from RAM
@@ -124,7 +126,27 @@ li t1,35
 beq s0,t1,1f # State 35 (US state 3): reset timer
 j 2f # None of the above, skip over the reset
 1: set_timer_to extensiontime
-2: li a7,133
+2:
+
+la t0,restartvalid
+lb t1,0(t0)
+beqz t1,1f # Check if the current state is something that can be restarted from
+sb x0,0(t0)
+la t0,currstate
+lb t1,0(t0)
+addi t1,t1,1 # State may be negative at the moment if we were on the last state
+andi t1,t1,0xfffffff0 # Find state 0 for the current country
+addi t1,t1,1 # Increment to state 1
+sb t1,0(t0) # Write the new state
+la t0,states
+addi t2,t1,1 # Landing pad label is state number + 1 (to avoid having any of them be 0)
+slli t2,t2,12
+sh2add t0,t1,t0 # Calculate the proper offset in the list of pointers (state number * 4 + base address)
+lw t0,0(t0) # Load the pointer
+jalr ra,t0,0 # And call that function
+1:
+
+li a7,133
 ecall # Check if there are more messages to process
 bnez a0,handler_digilines
 j handler_epilogue
@@ -215,6 +237,8 @@ digiline_send lightchannel,lightoffmsg
 digiline_send gatechannel,gateupmsg
 digiline_send bellchannel,belloffmsg
 digiline_send signalchannel,lightoffmsg
+la t0,restartvalid
+sb x0,0(t0)
 ret
 
 .align 2
@@ -258,6 +282,9 @@ destate6:
 lpad 7
 digiline_send gatechannel,gateupmsg
 set_timeri 2
+la t0,restartvalid
+li t1,1
+sb t1,0(t0)
 la t0,currstate
 li t1,-1
 sb t1,0(t0) # Next state should be 0
@@ -271,6 +298,8 @@ digiline_send lightchannel,lightoffmsg
 digiline_send gatechannel,gateupmsg
 digiline_send bellchannel,belloffmsg
 digiline_send signalchannel,lightflashredmsg
+la t0,restartvalid
+sb x0,0(t0)
 ret
 
 .align 2
@@ -314,6 +343,9 @@ ukstate6:
 lpad 23
 digiline_send signalchannel,lightflashredmsg
 digiline_send bellchannel,belloffmsg
+la t0,restartvalid
+li t1,1
+sb t1,0(t0)
 set_timeri 1
 ret
 
@@ -335,6 +367,8 @@ digiline_send lightchannel,lightoffmsg
 digiline_send gatechannel,gateupmsg
 digiline_send bellchannel,belloffmsg
 digiline_send signalchannel,lightoffmsg
+la t0,restartvalid
+sb x0,0(t0)
 ret
 
 .align 2
@@ -367,6 +401,9 @@ lpad 37
 digiline_send signalchannel,lightoffmsg
 digiline_send gatechannel,gateupmsg
 set_timeri 3
+la t0,restartvalid
+li t1,1
+sb t1,0(t0)
 la t0,currstate
 li t1,31
 sb t1,0(t0) # Next state should be 32 (US state 0)
@@ -379,6 +416,7 @@ gatedroptime: .byte 3
 activetime: .byte 15
 extensiontime: .byte 25
 traincounter: .word 0
+restartvalid: .byte 0
 
 uiunimplementedtrap: .asciz "\nUnimplemented trap!\nmcause: "
 uinmi: .asciz "\nUnexpected NMI!\nmncause: "