Siemens C541U, User Manual

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Semiconductor Group 3-3 1997-10-01
Memory Organization
C541U
standard special function register area and the mapped special function register area. One special
function register of the C541U (PCON1) is located in the mapped special function register area. All
other SFRs are located in the standard special function register area.
For accessing PCON1 in the mapped special function register area, bit RMAP in special function
register SYSCON must be set.
Special Function Register SYSCON (Address B1H) Reset Value : XX10XXXXB
As long as bit RMAP is set, a mapped special function register can be accessed. This bit is not
cleared by hardware automatically. Thus, when non-mapped/mapped registers are to be accessed,
the bit RMAP must be cleared/set by software, respectively each.
The registers, except the program counter and the four general purpose register banks, reside in the
special function register area. All SFRs with addresses where address bits 0-2 are 0 (e.g. 80H,
88H, 90H, 98H, ..., F8H, FFH) are bitaddressable.
The 75 special function registers (SFRs) in the SFR area include pointers and registers that provide
an interface between the CPU and the other on-chip peripherals. The SFRs of the C541U are listed
in table 3-1 and table 3-2. In table 3-1 they are organized in groups which refer to the functional
blocks of the C541U. Table 3-2 illustrates the contents of the SFRs in numeric order of their
addresses.
Bit Function
RMAP Special function register map bit
RMAP = 0 : The access to the non-mapped (standard) special function
register area is enabled.
RMAP = 1 : The access to the mapped special function register area
(PCON1) is enabled.
7 6 5 4 3 2 1 0
EALE RMAP – B1H SYSCON
Bit No. MSB LSB
– –
– –
–
The functions of the shaded bits are not described in this section.