From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 21 Jul 2019 17:44:11 +0000 (+0100)
Subject: add comment on what mantissas represent
X-Git-Tag: ls180-24jan2020~794
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=9c464db05483b76f7f59f77e5d339449eafb9207;p=ieee754fpu.git

add comment on what mantissas represent
---

diff --git a/src/ieee754/fpdiv/div0.py b/src/ieee754/fpdiv/div0.py
index 30d92c6d..90c98847 100644
--- a/src/ieee754/fpdiv/div0.py
+++ b/src/ieee754/fpdiv/div0.py
@@ -76,6 +76,12 @@ class FPDivStage0Mod(Elaboratable):
             # do conversion here, of both self.i.a and self.i.b,
             # into DivPipeCoreInputData dividend and divisor.
 
+            # the mantissas, having been de-normalised (and containing
+            # a "1" in the MSB) represent numbers in the range 0.5 to
+            # 0.9999999-recurring.  the min and max range of the
+            # result is therefore 0.4999999 (0.5/0.99999) and 1.9999998
+            # (0.99999/0.5).
+
             m.d.comb += [self.o.z.e.eq(self.i.a.e - self.i.b.e + 1),
                          self.o.z.s.eq(self.i.a.s ^ self.i.b.s)
                          self.o.dividend.eq(self.i.a.m), # TODO: check