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authorLars-Dominik Braun <lars@6xq.net>2019-03-02 17:23:59 +0100
committerLars-Dominik Braun <lars@6xq.net>2019-03-02 17:23:59 +0100
commit16ce87f6d2c7ba4d29a71e24200584366961f55d (patch)
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Correct number of EUMEL0 instructionsHEADmaster
Also reference EUMuLator.
-rw-r--r--internals.rst41
1 files changed, 24 insertions, 17 deletions
diff --git a/internals.rst b/internals.rst
index f9bfee4..d11dbce 100644
--- a/internals.rst
+++ b/internals.rst
@@ -38,21 +38,28 @@ only. A few internal registers like instruction counter, condition flag for
branching, several segment and status registers and a stack pointer exist.
The CISC instruction set was specifically designed for the high-level language
-ELAN. It includes arithmetic operations for ELAN’s primitive datatypes such as
-signed and unsigned integer as well as float (REAL) and operations for
-bytestrings (TEXT) and dataspaces. However the machine itself does not enforce
-datatypes at runtime. The usual control flow operations are accompanied by
-ELAN-specific call and return instructions. Special instructions for terminal
-and archive disk I/O, exception-like error handling and inter-process
-communication (IPC) are available.
-
-The 54 primary instructions can be encoded with two bytes. They consist of a
-6 bit opcode and one short operand. Whenever the latter is longer than 10 bit a
-long encoding using two bytes plus operands is used. This format also encodes
-42 secondary/special instructions.
-
-Read more instruction encoding details in chapter two of [kernel83]_ and the
-ELAN package `eumel coder`_.
-
-.. _eumel coder: system/eumel-coder/1.8.1/src/eumel%20coder%201.8.1.html
+ELAN.
+It includes arithmetic operations for ELAN’s primitive datatypes such as signed
+and unsigned integer as well as float (REAL) and operations for bytestrings
+(TEXT) and dataspaces.
+However the machine itself does not tag data and therefore doesn’t enforce
+types at runtime.
+The usual control flow operations are accompanied by ELAN-specific call and
+return instructions.
+Special instructions for terminal and archive disk I/O, exception-like error
+handling and inter-process communication (IPC) are available.
+
+Some of the 31 primary instructions can be encoded with just two bytes.
+They consist of a 6 bit opcode and one short operand.
+Whenever the latter uses more than 10 bit a long encoding consisting of two
+bytes opcode plus operands is used.
+This format also encodes 127 secondary and six special instructions.
+
+Details can be found in chapter two of [kernel83]_, the ELAN package `eumel
+coder`_, `this debugger’s sources and documentation`__ and a reimplementation
+of the EUMEL0 virtual machine, EUMuLator_.
+
+.. _eumel coder: src/system/eumel-coder/1.8.1/src/eumel%20coder%201.8.1.html
+.. _EUMuLator: https://github.com/PromyLOPh/EUMuLator
+__ src/devel/debugger/1.8.2/src/DEBUGGER.ELA.html