August 1993
14
Philips Semiconductors
Product specification
16-bit microcontroller
P90CE201
5.5
Stack format
The stack format for exception processing is similar to the 68010 (rather than the 68000) although the information stored
is not the same due to the different architecture. To handle this format the P90CE201 differs from the 68000 in that:
The stack format has changed.
The minimum number of words put into, or restored from, the stack is 4 (68010 compatible; not 3 as with the 68000).
The RTE instruction decides (with the aid of the 4 format bits) whether or not more information has to be restored. The
P90CE201 long format is used for bus error and address error exceptions; all other exceptions use the short format.
If another format code, other than one of the two listed above, is detected during the restore action, a Format Error
occurs.
If the user wants to finish the instruction in which the bus or address error occurred, the P90CE201 format must be used
on RTE. If no changes to the stack are required during exception processing, the stack format is transparent to the user.
5.5.1
L
ONG AND SHORT STACK FORMATS
Fig.7 Stack format.
SR
PCH/PCL
FORMAT
Status Register.
Program Counter High/Low Word.
Indicating either a short stack
(only the first 4 words), or the long
stack format for bus and address
error exceptions. See Fig.9.
The vector number of the
exception in the vector table; e.g.
2 for a bus error and 3 for an
address error. See Fig.9.
Special Status Word; see Fig.8.
Current Move Multiple Mask.
In the event of a faulty write cycle,
the data can be found here.
The address used during the faulty
bus cycle.
Data that has been read prior to
the faulty cycle can in some cases
be found here.
Holds the current instruction
being executed.
Holds either the present
instruction being executed or the
prefetched instruction.
VECTOR NUMBER
SSW
MM
TDPH/TDPL
TPFH/TPFL
DBINH/DBINL
IR
IRC
handbook, 4 columns
Short
Stack
Format
FORMAT (4 bits)
VECTOR NUMBER
Long
Stack
Format
SR
PCH
PCL
SSW
MM
INTERNAL INFORMATION
INTERNAL INFORMATION
TPDH
TPFL
DBINH
DBINL
INTERNAL INFORMATION
IR
IRC
TPFH
TPDL
MCD512