From 6df6071a9aa7cc813d1efc93747493b4f71409c7 Mon Sep 17 00:00:00 2001
From: Aaron Taylor <ataylor@subgeniuskitty.com>
Date: Fri, 25 Dec 2020 06:37:54 -0800
Subject: [PATCH] Initial framework for C code.

---
 Makefile    |  5 ++---
 bootstrap.s |  6 ++++++
 memtest.c   | 21 +++++++++++++++++++++
 pdp11.c     | 34 ++++++++++++++++++++++++++++++++++
 pdp11.h     | 10 ++++++++++
 pdp11.ld    | 25 +++++++++++++++++++++++++
 6 files changed, 98 insertions(+), 3 deletions(-)
 create mode 100644 bootstrap.s
 create mode 100644 memtest.c
 create mode 100644 pdp11.c
 create mode 100644 pdp11.h
 create mode 100644 pdp11.ld

diff --git a/Makefile b/Makefile
index 2d43f29..c66d625 100644
--- a/Makefile
+++ b/Makefile
@@ -42,10 +42,9 @@ all: aout
 
 aout: 
 	$(AS) $(AS_FLAGS) -o bootstrap.o bootstrap.s
-	$(CC) $(CC_FLAGS) -o cstart.o cstart.c
 	$(CC) $(CC_FLAGS) -o pdp11.o pdp11.c
-	$(CC) $(CC_FLAGS) -o hello.o hello.c
-	$(LD) $(LD_FLAGS) bootstrap.o cstart.o pdp11.o hello.o -o program.out
+	$(CC) $(CC_FLAGS) -o memtest.o memtest.c
+	$(LD) $(LD_FLAGS) bootstrap.o pdp11.o memtest.o -o program.out
 
 clean:
 	@rm -rf *.o *.out *.pdp11 *.bin *.core
diff --git a/bootstrap.s b/bootstrap.s
new file mode 100644
index 0000000..3e30f65
--- /dev/null
+++ b/bootstrap.s
@@ -0,0 +1,6 @@
+.globl _start
+
+_start:
+    mov $020000,sp
+    jsr pc,_memtest
+    halt
diff --git a/memtest.c b/memtest.c
new file mode 100644
index 0000000..e3bf460
--- /dev/null
+++ b/memtest.c
@@ -0,0 +1,21 @@
+#include "pdp11.h"
+
+void
+memtest(void)
+{
+    wait(01000);
+    putch('H');
+    putch('e');
+    putch('l');
+    putch('l');
+    putch('o');
+    putch(',');
+    putch(' ');
+    putch('W');
+    putch('o');
+    putch('r');
+    putch('l');
+    putch('d');
+    putch('!');
+    putch('\n');
+}
diff --git a/pdp11.c b/pdp11.c
new file mode 100644
index 0000000..c96ddf9
--- /dev/null
+++ b/pdp11.c
@@ -0,0 +1,34 @@
+#include <stdint.h>
+
+/*
+ * Polled console I/O
+ */
+
+#define RCSR (*((volatile uint16_t *)0177560))
+#define RBUF (*((volatile uint16_t *)0177562))
+#define XCSR (*((volatile uint16_t *)0177564))
+#define XBUF (*((volatile uint16_t *)0177566))
+
+void
+putch(uint16_t c)
+{
+    while((XCSR && 0200) == 0) continue;
+    XBUF = c;
+}
+
+uint16_t
+getch(void)
+{
+    while((RCSR && 0200) == 0) continue;
+    return RBUF;
+}
+
+/*
+ * Busy-loop
+ */
+
+void
+wait(uint16_t count)
+{
+    while (count--) continue;
+}
diff --git a/pdp11.h b/pdp11.h
new file mode 100644
index 0000000..1e55595
--- /dev/null
+++ b/pdp11.h
@@ -0,0 +1,10 @@
+#ifndef PDP11_STDIO_H
+#define PDP11_STDIO_H
+
+#include <stdint.h>
+
+void putch(uint16_t);
+uint16_t getch(void);
+void wait(uint16_t);
+
+#endif /* PDP11_STDIO_H */
diff --git a/pdp11.ld b/pdp11.ld
new file mode 100644
index 0000000..3affcb0
--- /dev/null
+++ b/pdp11.ld
@@ -0,0 +1,25 @@
+OUTPUT_FORMAT("a.out-pdp11")
+ENTRY(start)
+phys = 00001000;
+SECTIONS
+{
+  .text phys : AT(phys) {
+    code = .;
+    *(.text)
+    *(.rodata)
+    . = ALIGN(0100);
+  }
+  .data : AT(phys + (data - code))
+  {
+    data = .;
+    *(.data)
+    . = ALIGN(0100);
+  }
+  .bss : AT(phys + (bss - code))
+  {
+    bss = .;
+    *(.bss)
+    . = ALIGN(0100);
+  }
+  end = .;
+}
-- 
2.20.1