From 33e4744d1c73c9f5512abb4010e4cc81763ab3a2 Mon Sep 17 00:00:00 2001
From: cheapie <cheapiephp@gmail.com>
Date: Fri, 19 Jun 2026 22:38:28 -0500
Subject: Add machine timer interrupt

---
 assembly/multitask/Makefile        |  24 +++++++++++++++
 assembly/multitask/multitask.S     |  61 +++++++++++++++++++++++++++++++++++++
 assembly/multitask/multitask.elf   | Bin 0 -> 5608 bytes
 assembly/multitask/multitask.hex   |  12 ++++++++
 assembly/multitask/multitask.o     | Bin 0 -> 1812 bytes
 assembly/multitask/rvcontroller.ld |   1 +
 6 files changed, 98 insertions(+)
 create mode 100644 assembly/multitask/Makefile
 create mode 100644 assembly/multitask/multitask.S
 create mode 100755 assembly/multitask/multitask.elf
 create mode 100644 assembly/multitask/multitask.hex
 create mode 100644 assembly/multitask/multitask.o
 create mode 120000 assembly/multitask/rvcontroller.ld

(limited to 'assembly/multitask')

diff --git a/assembly/multitask/Makefile b/assembly/multitask/Makefile
new file mode 100644
index 0000000..bb51bce
--- /dev/null
+++ b/assembly/multitask/Makefile
@@ -0,0 +1,24 @@
+MARCH ?= rv32imacbzicntr_zicond_zicsr_zifencei_zihintpause_zilsd_zclsd_zabha_zacas_zbkb_zbkx_zcb_zcmp_zcmt
+
+.PHONY: all dump load clean
+
+all: multitask.hex
+
+multitask.o: multitask.S
+	riscv32-none-elf-as -I../rvcontroller-libraries -march=${MARCH} -o multitask.o multitask.S
+
+multitask.elf:  multitask.o
+	riscv32-none-elf-ld -T rvcontroller.ld --no-warn-rwx-segments -o multitask.elf multitask.o
+
+dump: multitask.elf
+	riscv32-none-elf-objdump -d multitask.elf
+
+multitask.hex: multitask.elf
+	riscv32-none-elf-objcopy -O ihex multitask.elf multitask.hex
+
+load: multitask.hex
+	bash -c "wl-copy < multitask.hex"
+
+clean:
+	rm -f multitask.hex multitask.elf multitask.o
+
diff --git a/assembly/multitask/multitask.S b/assembly/multitask/multitask.S
new file mode 100644
index 0000000..d34bf5f
--- /dev/null
+++ b/assembly/multitask/multitask.S
@@ -0,0 +1,61 @@
+la t0,handler
+csrw mtvec,t0 # Set trap handler address and mode (0/direct)
+li t0,0x400
+csrc mstatush,t0 # Enable trap handler
+li t0,0x80
+csrw mie,t0 # Enable machine timer interrupt and disable others
+la t1,mmio
+csrw 0x801,t1 # Set MMIO base address
+lw t0,2(t1) # Load current mtime
+addi t0,t0,1
+sw t0,10(t1) # Set mtimecmp for 1 second in the future
+csrsi mstatus,8 # Enable interrupts globally
+li t0,0x80
+csrs mstatus,t0 # Make sure MPIE is set too
+
+
+
+task1:
+li a0,1
+li a7,1
+ecall
+j task1
+
+task2:
+li a0,2
+li a7,1
+ecall
+j task2
+
+
+.balign 4
+handler:
+lw t0,2(t1) # Load current mtime
+addi t0,t0,1
+sw t0,10(t1) # Set mtimecmp for 1 second in the future
+la t0,currenttask
+lw t2,0(t0) # Get current task number
+addi t2,t2,1 # Flip to the other task
+andi t2,t2,1
+sw t2,0(t0) # Write the number back
+beqz t2,handler_return1
+j handler_return2
+
+handler_return1:
+la a0,task1
+csrw mepc,a0 # Set return address to start of task 1
+li t0,0x400
+csrc mstatush,t0
+mret
+
+handler_return2:
+la a0,task2
+csrw mepc,a0 # Set return address to start of task 2
+li t0,0x400
+csrc mstatush,t0
+mret
+
+
+currenttask: .word 1
+
+mmio:
diff --git a/assembly/multitask/multitask.elf b/assembly/multitask/multitask.elf
new file mode 100755
index 0000000..dafe381
Binary files /dev/null and b/assembly/multitask/multitask.elf differ
diff --git a/assembly/multitask/multitask.hex b/assembly/multitask/multitask.hex
new file mode 100644
index 0000000..7495df7
--- /dev/null
+++ b/assembly/multitask/multitask.hex
@@ -0,0 +1,12 @@
+:1000000097020000938242057390523093020040A1
+:1000100073B002319302000873904230170300005E
+:1000200013032309731013808322230085022325E1
+:100030005300736004309302000873A0023005453A
+:10004000854873000000E5BF09458548730000003E
+:10005000E5BF010083222300850223255300970278
+:1000600000009382C20483A30200850393F313006C
+:1000700023A072006383030029A81705000013055D
+:1000800045FC731015349302004073B002317300C5
+:10009000203017050000130565FB7310153493021B
+:1000A000004073B0023173002030010000000100F5
+:00000001FF
diff --git a/assembly/multitask/multitask.o b/assembly/multitask/multitask.o
new file mode 100644
index 0000000..6a94422
Binary files /dev/null and b/assembly/multitask/multitask.o differ
diff --git a/assembly/multitask/rvcontroller.ld b/assembly/multitask/rvcontroller.ld
new file mode 120000
index 0000000..bc01402
--- /dev/null
+++ b/assembly/multitask/rvcontroller.ld
@@ -0,0 +1 @@
+../../rvcontroller.ld
\ No newline at end of file
-- 
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