Memory; Program Memory; Data Memory - STC micro STC8A8K64D4 Series Reference Manual

STC8A8K64D4 Series Manual

7 Memory

The STC8A8K64D4 series of microcontrollers have separate address spaces for Program Memory and Data Memory.
Since no bus is provided for accessing external program memory, all program memory for all microcontrollers is on-chip
Flash memory. The microcontrollers can not access external program memory.
Large-capacity data memory is integrated in STC8A8K64D4 series of microcontrollers. The data memory inside the
STC8A8K64D4 series of microcontrollers is physically and logically separated into two address spaces: 256 bytes of internal
RAM and internal extended RAM. The addresses of the high 128 bytes of internal RAM and special function registers (SFRs)
overlap. They can be accessed through different addressing modes in actual use.

7.1 Program Memory

Program memory is used to store user programs, data, tables and other information.
64K bytes of Flash program memory is integrated in
After the microcontroller resets, the content of the Program Counter (PC) is 0000H, and the CPU begins to execute
program from 0000H of Program Memory. The entry addresses of interrupt service routines, which are also called interrupt
vectors, are also located in the program memory. Each interrupt has a fixed entry address in Program Memory. When an
interrupt occurs and gets response, the microcontroller will automatically jump to its corresponding interrupt entry address to
execute the service routine. The entry address of the interrupt service routine for the external interrupt 0 (INT0) is 0003H, the
entry address for the timer / counter 0 (TIMER0) interrupt service routine is 000BH, and the entry address for the interrupt
service routine for the external interrupt 1 (INT1) is 0013H. The counter/counter 1 (TIMER1) interrupt service routine's entry
address is 001BH. More interrupt service routine entry address (interrupt vector), please refer to interrupt chapter.
The interval of adjacent interrupt entry addresses is only 8 bytes, which is not enough to save the complete interrupt
service routine in general, so an unconditional jump instruction is stored in the the interrupt vector to jump to the space where
the real interrupt service routine is stored, then execute interrupt service routine.
All STC8A8K64D4 series of microcontrollers integrate Flash data memory (EEPROM). The EEPROM is read or written
in byte, and is erased in page of 512bytes. It can be repeatedly programmed and erased over 100,000 times, which improves
the flexibility and convenience of use.

7.2 Data Memory

The RAM integrated in the STC8A8K64D4 series of microcontrollers can be used to store intermediate results and
process data during program execution.
Family of microcontrollers
STC8A8K64D4-64Pin/48Pin
FFFFH
64K
...
001BH
0013H
000BH
0003H
0000H
Internal direct access RAM
(DATA)
128 bytes
STC8A8K64D4-64Pin/48Pin
Interrupt vectors
Entry address after program reset
Internal indirect access
RAM (IDATA)
128 bytes
-
family of microcontrollers.
On-chip extended
RAM (XDATA)
8192 bytes
- 102 -