z8f083a ZiLOG Semiconductor, z8f083a Datasheet - Page 141

• Manufacturer Part Number: z8f083a
• Description: High-performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

Non Volatile Data Storage
Operation
NVDS Code Interface
PS026308-1207
Note:
Byte Write
The Z8 Encore! F083A Series devices contain a Non Volatile Data Storage (NVDS)
element of up to 100 bytes. This memory can perform over 100,000 write cycles.
The NVDS is implemented by special purpose Zilog software stored in areas of program
memory not accessible to you. These special purpose routines use the Flash memory to
store the data. The routines incorporate a dynamic addressing scheme to maximize the
write/erase endurance of the Flash.
Different members of the Z8 Encore! F083A Series feature multiple NVDS array sizes. For
more details, see
Two routines are required to access the NVDS, a write routine and a read routine. Both of
these routines are accessed with a
program memory accessible to you. Both the NVDS address and data are single-byte
values. In order NOT to disturb the user code, these routines save the working register set
before using it, so 16 bytes of stack space is needed to preserve the site. After finishing the
call to these routines, the working register set of the user code is recovered.
During both read and write accesses to the NVDS, interrupt service is NOT disabled. Any
interrupts that occur during the NVDS execution must not disturb the working register and
existing stack contents; or else the array becomes corrupted. Disabling interrupts before
executing NVDS operations is recommended.
Use of the NVDS requires 16 bytes of available stack space. The contents of the working
register set are saved before calling NVDS read or write routines.
For correct NVDS operation, the Flash frequency registers must be programmed based on
the system clock frequency. See
Registers
To write a byte to the NVDS array, the user code must first push the address, then the data
byte onto the stack. The user code issues a
on page
Z8 Encore! F083A Series Family Part Selection Guide
110.
Flash Operation Timing Using the Flash Frequency
CALL
instruction to a pre-defined address outside of the
CALL
instruction to the address of the Byte
Z8 Encore!
Product Specification
Non Volatile Data Storage
®
on page 2.
F083A Series
129