122-32000 Parallax Inc, 122-32000 Datasheet - Page 97

• Manufacturer Part Number: 122-32000
• Description: MANUAL PROPELLER
• Manufacturer: Parallax Inc

Specifications of 122-32000

• Accessory Type: Manual
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: Propeller Education (PE) Kit
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Cogs (Processors)
The Propeller has eight identical processors, called cogs. Each cog can be individually set to
run or stop at any time as directed by the application it is running. Each cog can be
programmed to run independent tasks or cooperative tasks with other cogs, as needed, and
this can change as desired during the application’s run time.
But we didn’t specify which cog(s) to run in our Output.spin example, so how did it work?
For a review, you could read Boot Up Procedure, page 18, and Run-Time Procedure, page 18,
in Chapter 1, but we’ll discuss it a bit more here.
For our example, upon power-up, the Propeller chip starts the first processor (Cog 0) and
loads it with a built-in Boot Loader program. The Boot Loader program is copied from the
Propeller chip’s ROM into Cog 0’s internal RAM memory. Cog 0 then runs the Boot Loader
program in its internal memory and the Boot Loader soon determines it should copy user-
code from the external EEPROM. So Cog 0 copies the entire 32 K byte EEPROM contents
into the Propeller chip’s 32 K byte main RAM memory (separate from the cog’s internal
memory). Then the Boot Loader program makes Cog 0 reload itself with the built-in Spin
Interpreter; the Boot Loader program in Cog 0 halts at this point while it is being overwritten
with the Spin Interpreter program.
Now, Cog 0 is running the Spin Interpreter, which fetches and executes our application’s
code from main memory (RAM). This is shown in Figure 3-9. Since our application consists
Interpreter
Application
Main RAM
ROM
...
Figure 3-9: Running
Output.spin
Notice that the Spin
Interpreter, not the
Spin Application, is
loaded into Cog RAM.
The Spin Application
resides in Main RAM
and is interpreted by
the Spin Interpreter
program that is
running in the cog.
Propeller Manual v1.0 · Page 97