docs, removed assert about moving paper backwards, which was violated…

… by PTEST

docs/source/log.rst

@@ -622,3 +622,11 @@ be write protected. But write protect does apparently not prevent renaming.
   :align: center
 
   Files SCR, DINDEX and FRENKB renamed to XXX, XXXXXX, XXXXXB using 'ALTER' program
+
+Changes to disks, such as renaming and write protection is **not written to disk** so
+it is safe to experiment.
+
+The emulated system now comes preloaded with two floppy images: datamuseum and
+debugdisk. The first has good integrity the second has a lot of bad tracks so
+most programs will fail to load and execute. Some good files are: SCR, ALTER,
+DISPTEST, PTEST, COPY

src/devices/printer.py

@@ -43,6 +43,7 @@ def ctrl_06(self, value: int):
         #print(f'SI printer ctrl: move {dir} {v:6.2f} cm. pos ({x:6.2f}, {y:6.2f})')
 
 
+
     def ctrl_07(self, value: int):
         self.poshi2 = value & 0x3
         desc = ''
@@ -64,7 +65,7 @@ def ctrl_07(self, value: int):
         if value & 0x04:
             self.dir[0] = - self.dir[0]
             self.dir[1] = - self.dir[1]
-            assert self.dir[1] >= 0
+            #assert self.dir[1] >= 0, self.dir[1] # fails for PTEST program
             desc += 'reverse '
         else:
             desc += 'forward '