Rainbow Electronics T48C862-R4 - Manual (Page 15)

15
T48C862-R4
4551B–4BMCU–02/03
The corresponding memory map is shown in Figure 4. Look-up tables of constants can
also be held in ROM and are accessed via the microcontrollers’ built-in table instruction.
Figure 10. ROM Map of the Microcontroller Block
RAM The microcontroller block contains a 256 x 4-bit wide static random access memory
(RAM), which is used for the expression stack. The return stack and data memory are
used for variables and arrays. The RAM is addressed by any of the four 8-bit wide RAM
address registers SP, RP, X and Y.
Expression Stack The 4-bit wide expression stack is addressed with the expression stack pointer (SP). All
arithmetic, I/O and memory reference operations take their operands, and return their
results to the expression stack. The microcontroller performs the operations with the top
of stack items (TOS and TOS-1). The TOS register contains the top element of the
expression stack and works in the same way as an accumulator. This stack is also used
for passing parameters between subroutines and as a scratch pad area for temporary
storage of data.
Return Stack The 12-bit wide return stack is addressed by the return stack pointer (RP). It is used for
storing return addresses of subroutines, interrupt routines and for keeping loop index
counts. The return stack can also be used as a temporary storage area.
The microcontroller instruction set supports the exchange of data between the top ele-
ments of the expression stack and the return stack. The two stacks within the RAM have
a user definable location and maximum depth.
EEPROM
(4 K x 8 bit)
Zero page
FFFh
7FFh
1FFh
000h
1F0h
1F8h
010h
018h
000h
008h
020h
1E8h
1E0h
S
C
A
LL addresses
140h
180h
040h
0C 0h
008h
$AUTOSLEEP
$RESET
INT0
INT1
INT2
INT3
INT4
INT5
INT6
INT7 1E0h
1C 0h
100h
080h
page
000h