st20-gp6 STMicroelectronics, st20-gp6 Datasheet - Page 52

• Manufacturer Part Number: st20-gp6
• Description: Gps Processor
• Manufacturer: STMicroelectronics

ST20-GP6
The contents of these addresses can be accessed via ldtraph , sttraph , ldtrapped and sttrapped
instructions.
8.2
There is 128K bytes of mask ROM on-chip. This is mapped to the upper 128K of bank 3
(addresses #7FFE0000 to #7FFFFFFF).
If mask ROM is not programmed, internal ROM is disabled and external ROM is used.
When the processor boots from ROM, it jumps to a boot program held in ROM with an entry point 2
bytes from the top of memory at #7FFFFFFE. These 2 bytes are used to encode a negative jump
of up to 256 bytes down in the ROM program. For large ROM programs it may then be necessary
to encode a longer negative jump to reach the start of the routine.
8.3
On-chip peripherals are mapped to addresses in the address range #00000000 to #3FFFFFFF).
They can only be accessed by the device access instructions (see Table 7.19). When used with
addresses in this range, the device instructions access the on-chip peripherals rather than external
memory. For all other addresses the device instructions access memory. Standard load/store
instructions to these addresses will access external memory.
Each on-chip peripheral occupies a 4K block, see the following memory map.
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Boot ROM
Internal peripheral space