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3.4 B R E A D B O A R D P O R T ADDRESSING S C H E M E S
There are two groups o f commands:
- p o r t numbers
- c a r d ports
The software commands in the local command set that do not begin with a 'c' use straight
port numbers. P o r t numbers run from 0 to 2'5 - 1 (32767). P o r t space is divided into 16
cards. E a c h card potentially has 2048 ports. T h i s means a card with its address set to
0 has ports 0 to 2047. A n d , w i t h its address set to 1. i t has ports 2048 t o 4095, etc.
Hardware i s o n l y provided f o r the lower twelve ports on each card. T h e user may
provide hardware for additional ports.
Another group of commands is available to perform the same functions, but accounts for
the offset of each group of ports on a card. These are the commands that start with a 'c'.
This may be more convenient for a system with a large number o f breadboard modules.
These commands use a 'card' ( 0 to 15) and a 'cport' ( 0 to 2047) t o locate the actual
address.
When using one breadboard only, t h e card address can be set to 0, and the first set of
commands can be used. T h i s has the advantage o f shorter commands.
Example:
The command "setbit(4096,0);" and "csetbit(2,0,0);" both set port 0, bit 0 on card
number 2 to 1.
3.5 B A S E N U M B E R S
Numbers used f o r cards, ports, values, etc. can be represented i n any o f the standard
bases. T h e default base is decimal. H e x numbers are represented by a leading '#F1' in
the number. F o r example, 2 5 5 is represented by #HFF. U p p e r case and lower case are
the same and can be mixed freely. B i n a r y numbers are represented by a leading '#B'.
For example, 255 in binary is #B11111111. O c t a l numbers are represented by a leading
'#Q1. F o r example, 255 i n octal is #Q377. A l l base indicators can be either upper or
lower case. C -style hex and octal numbers are also accepted.
Commands that return values can have the values return in binary, octal, decimal or hex.
The format of the returned value is determined by the base command. T h i s only affects
returned values.
3-4
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