UM10147_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 28 April 2008
11 of 134
NXP Semiconductors
UM10147
P89LPC952/954 User manual
1.3 Special function registers
Remark:
SFR accesses are restricted in the following ways:
•
User must
not
attempt to access any SFR locations not defined.
•
Accesses to any defined SFR locations must be strictly for the functions for the SFRs.
•
SFR bits labeled ‘-’, ‘0’ or ‘1’ can
only
be written and read as follows:
–
‘-’ Unless otherwise specified,
must
be written with ‘0’, but can return any value
when read (even if it was written with ‘0’). It is a reserved bit and may be used in
future derivatives.
–
‘0’
must
be written with ‘0’, and will return a ‘0’ when read.
–
‘1’
must
be written with ‘1’, and will return a ‘1’ when read.