App::Scheme79asm - assemble sexp to Verilog ROM for SIMPLE processor
use App::Scheme79asm; my $asm = App::Scheme79asm->new(type_bits => 3, addr_bits => 5); $asm->parse_and_print_verilog('(number 70)');
SIMPLE is a LISP processor defined in the 1979 Design of LISP-Based Processors paper by Steele and Sussman.
The SIMPLE processor expects input in a particular tagged-pointer format. This module takes a string containing a sequence of S-expressions. Each S-expression is a list of one of three types:
(tag value), for example
(symbol 2), represents a value to be put in memory (for example a number, or a symbol, or a variable reference). The value must be a number.
(tag list), where
list is of one of these three types, represents a tagged pointer. In this case,
list is (recursively) laid out in memory as per these rules, and a pointer to that location (and tagged
tag) is put somewhere in memory.
(tag list1 list2), where
list2 are of one of these three types (not necessarily the same type). In this case,
list2 are (recursively) laid out in memory such that
list1 is at position X and
list2 is at position X+1, and a pointer of type tag and value X is put somewhere in memory.
After this process the very last pointer placed in memory is moved to the special location 5 (which is where SIMPLE expects to find the expression to be evaluated).
In normal use a single S-expression will be supplied, representing an entire program.
tag is either a number, a type, or a primitive. The available types are:
- SYMBOL (syn. NUMBER)
- VAR (syn. VARIABLE)
- PROC (syn. PROCEDURE)
- IF (syn. COND, CONDITIONAL)
- QUOTE (syn. QUOTED)
The available primitives are:
The following methods are available:
- App::Scheme79asm->new([key => value, key => value, ...])
Create a new assembler object. Takes a list of keys and values, here are the possible keys:
A word is made of a type and an address, with the type occupying the most significant
type_bits(default 3) bits, and the address occupying the least significant
address_bits(default 8) bits. Therefore the word size is
type_bits + address_bits(default 11).
A pointer to the last used byte in memory (default 6). The program will be laid out starting with location
freeptr + 1.
The initial contents of the memory. Note that locations 4, 5, 6 will be overwritten, as will every location larger than the value of
The initial comments for memory entries.
$comment->[$i]is the comment for
$memory->[$i]. Note that the first 7 entries of this array will be overwritten with the default comments. This is useful when using custom initial memory contents and freeptr, because this key can be used to provide comments for the extra reserved locations in memory.
Parse a sequence of S-expressions and lay it out in memory. Can be called multiple times to lay out multiple sequences of S-expressions one after another.
Given an already-parsed sexp (meaning a Data::SExpression object), lay it out in memory. Can be called multiple times to lay out multiple sequences of S-expressions one after another.
Move the last pointer to position 5, and put the free pointer at position 4. After all sequences of S-expressions have been given to parse, this method should be called.
Print the length of the memory (as a big-endian 16-bit value), followed by the memory contents as a sequence of big-endian 16-bit values to the given filehandle (default STDOUT). Dies if
addr_bits + type_bitsis more than 16.
Big-endian 16-bit values can be decoded with
unpack 'n', $value.
Print a block of Verilog code assigning the memory contents to an array named
memto the given filehandle (default STDOUT).
- $asm->parse_and_print_binary16($string[, $fh])
Convenience method that calls parse($string), finish, and then print_binary16($fh).
- $asm->parse_and_print_verilog($string[, $fh])
Convenience method that calls parse($string), finish, and then print_verilog($fh).
Marius Gavrilescu, <email@example.com>
Copyright (C) 2018 by Marius Gavrilescu
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.24.3 or, at your option, any later version of Perl 5 you may have available.