Hardware Reference
In-Depth Information
Example 14.1
▼
Write an instruction sequence to remap the register block to $4000.
Solution:
The upper 5 bits of the INITRG register should be 01000. The following instruction
sequence will achieve the desired assignment:
movb
#$40,INITRG
nop
; wait for the remap to take effect
▲
SRAM can be remapped to any 2-kB boundary within the 64-kB memory space. The remap-
ping is controlled by the INITRM register. The contents of the INITRM are shown in Figure
14.2. Bits RAM15 to RAM11 determine the upper 5 bits of the base address for the system's
internal SRAM array. The INITRM register can be written into once in normal modes but many
times in special modes.
7
6
5
4
3
2
1
0
RAM 15
RAM 14
RAM 13
RAM 12
RAM 11
0
0
RAMHAL
base+$10
Value after
reset:
0
0
0
0
1
0
0
0
RAM15
,
RAM11: internal RAM map position
These bits determine the upper 5 bits of the base address for
the system's internal RAM array.
RAMHAL: RAM high-align
0 = aligns the RAM to the lowest address ($0000) of the
mappable space.
1 = aligns the RAM to the highest address ($FFFF) of the
mapping space.
Figure 14.2
■
RAM initialization register (INITRM)
The EEPROM block can be remapped to any 2-kB boundary. The remapping of EEPROM is
controlled by the INITEE register. The contents of this register are shown in Figure 14.3. The
EEPROM is activated by bit 0 of this register. Bits EE15 to EE11 determine the upper 5 bits of
the base address for the system's internal EEPROM array. The INITEE register can be written
any time.
A few registers are involved in the mapping control of more than one memory module. The
functions of these registers are described in this section.
M
ISCELLANEOUS
S
YSTEM
C
ONTROL
R
EGISTER
(MISC)
This register enables/disables the on-chip ROM (including flash memory and EEPROM)
and allows us to stretch the length of the external bus cycle. The contents of this register are
shown in Figure 14.4. The value of the ROMONE pin is latched to the ROMON bit of the
MISC register on the rising edge of the RESET signal. If the ROMONE signal is high when it is
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