Add a linker script and example uart echo program

1 files changed, 18 insertions, 0 deletions

diff --git a/echo.S b/echo.S
new file mode 100644
index 0000000..58b2573
--- /dev/null
+++ b/echo.S
@@ -0,0 +1,18 @@
+.section .text
+.globl _start
+
+.equ UART_DATA, 0
+.equ UART_STATUS, 1
+.equ UART_RX_READY = 0b10
+.equ UART_TX_READY = 0b01
+
+_start:
+    li a0, 0x1000
+
+loop:
+    lbu t0, UART_STATUS(a0)
+    andi t0, t0, UART_RX_READY
+    beqz t0, loop
+    lbu t0, UART_DATA(a0)
+    sb t0, UART_DATA(a0)
+    j loop