Z51F3220FNX Datasheet, PDF (52/312 Pages) Zilog, Inc. – Z8051 Series 8-Bit Microcontrollers

Z51F3220
Product Specification
8. Memory
The Z51F3220 addresses two separate address memory stores: Program memory and Data memory. The
logical separation of Program and Data memory allows Data memory to be accessed by 8-bit addresses, which
makes the 8-bit CPU access the data memory more rapidly. Nevertheless, 16-bit Data memory addresses can
also be generated through the DPTR register.
Z51F3220 provides on-chip 32k bytes of the ISP type flash program memory, which can be read and written to.
Internal data memory (IRAM) is 256 bytes and it includes the stack area. External data memory (XRAM) is 768
bytes and it includes 27 bytes of LCD display RAM.
8.1 Program Memory
A 16-bit program counter is capable of addressing up to 64k bytes, but this device has just 32k bytes program
memory space.
Figure 8-1 shows the map of the lower part of the program memory. After reset, the CPU begins execution from
location 0000H. Each interrupt is assigned a fixed location in program memory. The interrupt causes the CPU to
jump to that location, where it commences execution of the service routine. External interrupt 11, for example, is
assigned to location 000BH. If external interrupt 11 is going to be used, its service routine must begin at location
000BH. If the interrupt is not going to be used, its service location is available as general purpose program
memory. If an interrupt service routine is short enough (as is often the case in control applications), it can reside
entirely within that 8 byte interval. Longer service routines can use a jump instruction to skip over subsequent
interrupt locations, if other interrupts are in use.
PS029902-0212
PRELIMINARY
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