Address space is circular

Closes #40

1 files changed, 7 insertions, 1 deletions

diff --git a/src/intro.tex b/src/intro.tex
index b95c6b3..2629f6e 100644
--- a/src/intro.tex
+++ b/src/intro.tex
@@ -344,12 +344,18 @@ regardless of any subsequent extensions.
 
 \section{Memory}
 
-A RISC-V hart has a single byte-addressable address space for all memory
+A RISC-V hart has a single byte-addressable address space
+of $2^{XLEN}$ bytes for all memory
 accesses.  A {\em word} of memory is defined as \wunits{32}{bits}
 (\wunits{4}{bytes}).  Correspondingly, a {\em halfword} is \wunits{16}{bits}
 (\wunits{2}{bytes}), a {\em doubleword} is \wunits{64}{bits}
 (\wunits{8}{bytes}), and a {\em quadword} is \wunits{128}{bits}
 (\wunits{16}{bytes}).
+The memory address space is circular, so that the byte at address
+$2^{XLEN}-1$ is adjacent to the byte at address zero.  Accordingly, memory
+address computations done by the hardware ignore overflow and instead
+wrap around modulo $2^{XLEN}$.
+
 
 The execution environment determines the mapping of hardware resources into
 a hart's address space.