
Register and memory map ST72321xx-Auto
26/243 Doc ID 13829 Rev 1
3 Register and memory map
As shown in Figure 4, the MCU is capable of addressing 64 Kbytes of memories and I/O
registers.
The available memory locations consist of 128 bytes of register locations, up to 2 Kbytes of
RAM and up to 60 Kbytes of user program memory. The RAM space includes up to 256
bytes for the stack from 0100h to 01FFh.
The highest address bytes contain the user reset and interrupt vectors.
IMPORTANT: Memory locations marked as “Reserved” must never be accessed. Accessing
a reserved area can have unpredictable effects on the device.
Related documentation
Executing Code in ST7 RAM (AN 985)
Figure 4. Memory map
0000h
RAM
Program Memory
(60K or 32K)
Interrupt & Reset Vectors
HW Registers
0080h
007Fh
0FFFh
(see Tabl e 4 )
1000h
FFDFh
FFE0h
FFFFh
(see Tab l e 2 0 )
0880h
Reserved
087Fh
Short Addressing
RAM (zero page)
256 Bytes Stack
16-bit Addressing
RAM
0100h
01FFh
0080h
0200h
00FFh
or 087Fh
32 KBytes
8000h
60 KBytes
FFFFh
1000h
(2048 or 1024 Bytes)
or 067Fh
or 047Fh
Table 4. Hardware register map
Address Block Register label Register name Reset status Remarks
0000h
0001h
0002h
Port A
PAD R
PAD DR
PAO R
Port A Data Register
Port A Data Direction Register
Port A Option Register
00h
(1)
00h
00h
R/W
R/W
R/W
0003h
0004h
0005h
Port B
PBDR
PBDDR
PBOR
Port B Data Register
Port B Data Direction Register
Port B Option Register
00h
(1)
00h
00h
R/W
R/W
R/W
0006h
0007h
0008h
Port C
PCDR
PCDDR
PCOR
Port C Data Register
Port C Data Direction Register
Port C Option Register
00h
(1)
00h
00h
R/W
R/W
R/W
0009h
000Ah
000Bh
Port D
PDDR
PDDDR
PDOR
Port D Data Register
Port D Data Direction Register
Port D Option Register
00h
(1)
00h
00h
R/W
R/W
R/W
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