cop8cde9 National Semiconductor Corporation, cop8cde9 Datasheet - Page 16

• Manufacturer Part Number: cop8cde9
• Description: 8-bit Cmos Flash Microcontroller With 8k Memory, Virtual Eeprom, 10-bit A/d And Brownout Reset
• Manufacturer: National Semiconductor Corporation

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4.0 Functional Description
addresses 00F0 to 00FF of the upper base segment. No
RAM is located at the upper sixteen addresses (0070 to
007F) of the lower base segment.
Additional RAM beyond these initial 128 bytes, however, will
always be memory mapped in groups of 128 bytes (or less)
4.4.1 Virtual EEPROM
The Flash memory and the User ISP functions (see Section
5.7), provide the user with the capability to use the flash
program memory to back up user defined sections of RAM.
This effectively provides the user with the same nonvolatile
data storage as EEPROM. Management, and even the
amount of memory used, are the responsibility of the user,
however the flash memory read and write functions have
been provided in the boot ROM.
One typical method of using the Virtual EEPROM feature
would be for the user to copy the data to RAM during system
initialization, periodically, and if necessary, erase the page of
Flash and copy the contents of the RAM back to the Flash.
4.5 OPTION REGISTER
The Option register, located at address 0x3FFF (hex) in the
Flash Program Memory, is used to configure the user select-
able security, WATCHDOG, and HALT options. The register
can be programmed only in external Flash Memory program-
ming or ISP Programming modes. Therefore, the register
must be programmed at the same time as the program
memory. The contents of the Option register shipped from
the factory read 00 Hex.
The format of the Option register is as follows:
Bit 7
Reserved
Bit 6
SECURITY
Bit 5
Bit 4
Reserved
Bit 3
WATCH
Bit 2
DOG
HALT
Bit 1
(Continued)
FIGURE 7. RAM Organization
FLEX
Bit 0
16
at the data segment address extensions (XX00 to XX7F) of
the lower base segment. The additional 128 bytes of RAM in
this device are memory mapped at address locations 0100
through 017F.
Bits 7, 6 These bits are reserved and must be 0.
Bit 5
Bits 4, 3 These bits are reserved and must be 0.
Bit 2
Bit 1
Bit 0
= 1
= 0
= 1
= 0
= 1
= 0
= 1
= 0
Security enabled. Flash Memory read and write
are not allowed except in User ISP/Virtual E
mands. Mass Erase is allowed.
Security disabled. Flash Memory read and write
are allowed.
WATCHDOG feature disabled. G1 is a general
purpose I/O.
WATCHDOG
WATCHDOG output with weak pullup.
HALT mode disabled.
HALT mode enabled.
Execution following RESET will be from Flash
Memory.
Flash Memory is erased. Execution following RE-
SET will be from Boot ROM with the MICROWIRE/
PLUS ISP routines.
feature
enabled.
20022510
G1
pin
2
com-
is