Added misc file 'custom_bitstream.c' that creates paper tape with repeating memory...

diff --git a/custom_bitstream.c b/custom_bitstream.c
new file mode 100644 (file)
index 0000000..144a5ac
--- /dev/null
+++ b/custom_bitstream.c
@@ -0,0 +1,43 @@
+/*
+ * © 2020 Aaron Taylor <ataylor at subgeniuskitty dot com>
+ * See LICENSE.txt file for copyright and license details.
+ */
+
+/*
+ * Outputs a file compatible with PDP-11 paper tape loader.
+ * File will load memory with integer counting (ex: 0, 1, 2, ..., NUMWORDS-2, NUMWORDS-1).
+ * Load starts at 01000 and ends at 01000 + NUMWORDS - 1.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#define NUMWORDS 20000
+
+void main( int argc, char ** argv ) {
+    uint16_t * packet = malloc((2*NUMWORDS) + 16);
+    /*
+     *  +16 comes from:
+     *     3 for start of first packet header
+     *     1 for first checksum plus padding byte
+     *     4 for second packet header + checksum on empty packet
+     *     Then double because PDP-11 word is 2 byte.
+     */
+    packet[0] = 1;                  /* Standard header */
+    packet[1] = (2*NUMWORDS) + 6;   /* Size of packet, including header but excluding checksum */
+    packet[2] = 01000;              /* Address to load packet */
+    packet[NUMWORDS+3] = 0;         /* Empty checksum. SIMH complains but still loads the image. */
+    packet[NUMWORDS+4] = 1;         /* Start of next packet, standard header */
+    packet[NUMWORDS+5] = 6;         /* Size of packet (just the header since blank body */
+    packet[NUMWORDS+6] = 01000;     /* Blank body means start execution at this address */
+    packet[NUMWORDS+7] = 0;         /* Empty checksum. SIMH complains but still loads the image. */ 
+
+    uint16_t i;
+    for(i=0; i < NUMWORDS; i++) packet[i+3] = i; /* Start at 0 so first instruction halts machine */
+
+    FILE * fp;
+    fp = fopen("testimg.pdp11","w+");
+    fwrite(packet,(2*NUMWORDS)+16,1,fp);
+    fclose(fp);
+}