released lecture 2

commit 9d515861bb0c98d6fbdc74755a166f1b1a9a7c7c
Author: Chris Gregg <[email protected]>
Date:   Fri Jan 10 00:10:23 2025 -0800

    released lecture 2

Author: tofergregg

_data/unreleased.csv

@@ -17,7 +17,6 @@ permalink,title,released
 "/labs/projectlab1/","Lab 8: Project Team Meeting 1",false
 "/labs/projectlab2/","Lab 9: Project Team Meeting 2",false
 "/lectures/Arithmetic/","Number Representation and Arithmetic",false
-"/lectures/Assembly/","RISC-V assembly and machine code",false
 "/lectures/Ben/","Magic of Computer Systems",false
 "/lectures/C_Control/","From Assembly to C",false
 "/lectures/C_Functions/","C Functions",false

lectures/Assembly/README.md

@@ -0,0 +1,11 @@
+---
+released: true
+permalink: /lectures/Assembly/
+title: RISC-V assembly and machine code
+readings: |
+    + Here is a link to the [Ripes simulator](https://ripes.me/) demoed in lecture.
+    + Our [one-page guide to RISC-V](/guides/riscv-onepage).
+    + Enjoy Danny Cohen's article
+     [Holy Wars and a Plea for Peace](/readings/holywars.pdf) on the history of little-endian vs. big-endian.
+---
+

lectures/Assembly/code/add/README.md

@@ -0,0 +1,24 @@
+Demo of cross-development toolchain
+
+Assembly a one instruction program:
+
+    add    x3,x1,x2
+
+
+# assemble add.s to make an 'object file' add.o
+riscv64-unknown-elf-as add.s -o add.o
+
+# number of bytes in add.o
+ls -l add.o
+
+# convert the object file to a binary file
+riscv64-unknown-elf-objcopy add.o  add.bin -O binary
+
+# number of bytes in add.bin
+ls -l add.bin
+
+# "size" of add.o
+riscv64-unknown-elf-size add.o
+
+# print a hexdump of the binary
+hexdump -C add.bin

lectures/Assembly/code/add/add.s

@@ -0,0 +1,2 @@
+add x3,x1,x2
+addi a0,zero,21

lectures/Assembly/code/blink/Makefile

@@ -0,0 +1,4 @@
+run:
+	riscv64-unknown-elf-as blink.s -o blink.o
+	riscv64-unknown-elf-objcopy blink.o -O binary blink.bin
+	mango-run blink.bin

lectures/Assembly/code/blink/blink.s

@@ -0,0 +1,18 @@
+# File: blink.s
+# -------------
+# blink LED connected to GPIO PB0
+
+    lui     a0,0x2000       # a0 holds base addr PB group = 0x2000000
+    addi    a1,zero,1       # a1 holds constant 1
+    sw      a1,0x30(a0)     # config PB0 as output
+
+loop:
+    xori    a1,a1,1         # xor ^ 1 invert a1
+    sw      a1,0x40(a0)     # set data value of PB0 to a1
+
+    lui     a2,0x3f00       # a2 = init countdown value
+delay:                      # busy loop to wait for a while
+    addi    a2,a2,-1        # decrement a2
+    bne     a2,zero,delay   # keep counting down until a2 is zero
+
+    j       loop            # back to top of outer loop

lectures/Assembly/code/on/doit

@@ -0,0 +1,2 @@
+riscv64-unknown-elf-as on.s -o on.o
+riscv64-unknown-elf-objcopy on.o -O binary on.bin

lectures/Assembly/code/on/on.s

@@ -0,0 +1,25 @@
+#false File on.s
+# ---------
+# turn on LED connected to GPIO PB0
+
+# configure PB0 for output
+#
+# Base address of GPIO peripheral is 0x02000000
+# PB0 configured by config0 register of PB group
+# PB config0 register is at offset 0x30 from GPIO base
+
+    lui     a0,0x2000       # GPIO base address in a0
+    addi    a1,zero,1       # constant 1 for output in a1
+    sw      a1,0x30(a0)     # config PB0 as output
+
+# set PB0 value to 1
+#
+# PB0 value is bit 0 in PB data register
+# PB data register is at offset 0x40 from GPIO base
+
+# a0 set to gpio base above, a1 has value 1
+    sw      a1,0x40(a0)     # turn on PB0
+
+# infinite loop
+loop:
+    j loop