Texas Instruments 990 Operation Manual page 18

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A diagram of the memory configuration is shown in figure 1-4. The numbers at the left are byte
addresses and are given for the minimum memory configuration of 4K words of user and 4K
words of system memory.
1.4.1.2 System Software Loaders. Loading of programs or program modules is accomplished
with one or more of the four available loaders provided in the system software:
• Standard 990 object loader. Loads a program in standard 990 object code. The loader
resides in a 256-word ROM. One of the standard loader's functions is used to load
overlays into the monitor transient area.
• Compressed absolute format loader. Loads a program that has been stored in compressed
absolute format. The loader is an overlay that must be resident in the monitor transient
area.
• Upfront loader (PX9UFLJ. Loads a program in compressed absolute format code. The
loader must be located immediately in front of the beginning of the compressed absolute
format code. The 733 ASR ROM (standard) loader loads the upfront loader, which in
tum loads the compressed absolute format code.
• Relocating linking loader (PX9LALJ. PX9LAL which must be resident in the monitor
transient area, loads program modules in object code, modifies memory addresses in
the modules, and links the modules. The program code may specify absolute memory
locations or specify relocatable memory locations that allow the entire. program
module to be placed in any sufficiently large available memory area.
These loaders handle either conventional object code or object code in compressed absolute
format. The compressed absolute format code allows faster loading than with standard 990
object code. Object code formats are described in detail in Section VI.
1.4.2 DEBUG MONITOR (PX9MTP). PX9MTP, the control program and system executive for
the software system, occupies 4K words of memory.
1.4.2.1 Overview. PX9MTP is a modular program that consists of five major divisions:
• I/O executive
• Keyboard command processor
• Supervisor call interface
• Keyboard commands
• Debug commands
• System control commands
• Transient area
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Digital Systems Division .