GMP4 MPU information

[Ludis Langens]

The architecture of the GMP4 processor chip (used in the GM P4
generation of ECMs) is almost the same as a Motorola 68HC11 with the
following exceptions:

Bits 7 and 6 of the CCR (S and X in an 'HC11) always read as 1's.
The STOP instruction ($CF) is missing.
The XGDX instruction ($8F) is missing.
The XGDY instruction ($18 8F) is missing.

The interrupt vector map is:
 $FFF0  SWI instruction
 $FFF2  Internal interrupt (UART & periodic interrupt)
 $FFF4  External interrupt
 $FFF6  Illegal instruction
 $FFF8  Bus reset (any read or write to $6000 through $6FFF)
 $FFFA  Watchdog reset
 $FFFC  Clock monitor reset
 $FFFE  Power on and external reset

None of the 'HC11 I/O is present.  The GMP4 has it's own I/O registers
mapped to $4000 through $400F.

On-chip SRAM exists from $0000 through $01FF.  $0000 through $00FF is
retained by a standby power supply.  Data in $0100 through $01FF will be
lost when the main power supply shuts off.


An MPU with the part number 16034980 was used to collect the above data.
Several other part numbers are used interchangeably.  They may have
differences.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/