UPSD33XX Datasheet, PDF (31/231 Pages) STMicroelectronics – Fast 8032 MCU with Programmable Logic

uPSD33xx
Indexed Addressing
This mode is used for the MOVC instruction which
allows the 8032 to read a constant from program
memory (not data memory). MOVC is often used
to read look-up tables that are embedded in pro-
gram memory. The final address produced by this
mode is the result of adding either the 16-bit PC or
DPTR value to the contents of the accumulator.
The value in the accumulator is referred to as an
index. The data fetched from the final location in
program memory is stored into the accumulator,
overwriting the index value that was previously
stored there. For example:
MOVC A, @A+DPTR; Move code byte relative to
; DPTR into accumulator
MOVC A, @A+PC ; Move code byte relative to PC
; into accumulator
Relative Addressing
This mode will add the two’s-compliment number
stored in the second byte of the instruction to the
program counter for short jumps within +128 or –
127 addresses relative to the program counter.
This is commonly used for looping and is very effi-
cient since no additional bus cycle is needed to
fetch the jump destination address. For example:
SJMP 34h
; Jump 34h bytes ahead (in program
; memory) of the address at which
; the SJMP instruction is stored. If
; SJMP is at 1000h, program
; execution jumps to 1034h.
Absolute Addressing
This mode will append the 5 high-order bits of the
address of the next instruction to the 11 low-order
bits of an ACALL or AJUMP instruction to produce
a 16-bit jump address. The jump will be within the
same 2K byte page of program memory as the first
byte of the following instruction. For example:
AJMP 0500h
; If next instruction is located at
; address 4000h, the resulting jump
; will be made to 4500h.
Long Addressing
This mode will use the 16-bits contained in the two
bytes following the instruction byte as a jump des-
tination address for LCALL and LJMP instructions.
For example:
LJMP 0500h
; Unconditionally jump to address
; 0500h in program memory
Bit Addressing
This mode allows setting or clearing an individual
bit without disturbing the other bits within an 8-bit
value of internal SRAM. Bit Addressing is only
available for certain locations in 8032 DATA and
SFR memory. Valid locations are DATA address-
es 20h - 2Fh and for SFR addresses whose base
address ends with 0h or 8h. (Example: The SFR,
IE, has a base address of A8h, so each of the eight
bits in IE can be addressed individually at address
A8h, A9h, ...up to AFh.) For example:
SETB AFh
; Set the individual EA bit (Enable All
; Interrupts) inside the SFR Register,
; IE.
31/231