Datasheet

© 2009 Microchip Technology Inc. DS22233A-page 33
MCP434X/436X
4.2.1 NON-VOLATILE MEMORY
(EEPROM)
This memory can be grouped into two uses of
non-volatile memory. These are:
• General Purpose Registers
• Non-Volatile Wiper Registers
The non-volatile wipers starts functioning below the
devices V
POR
/V
BOR
trip point.
4.2.1.1 General Purpose Registers
These locations allow the user to store up to 5 (9-bit)
locations worth of information.
4.2.1.2 Non-Volatile Wiper Registers
These locations contain the wiper values that are
loaded into the corresponding volatile wiper register
whenever the device has a POR/BOR event. There are
four registers, one for each resistor network.
The non-volatile wiper register enables stand-alone
operation of the device (without Microcontroller control)
after being programmed to the desired value.
4.2.1.3 Factory Initialization of Non-Volatile
Memory (EEPROM)
The Non-Volatile Wiper values will be initialized to
mid-scale value. This is shown in Table 4-2.
The General purpose EEPROM memory will be
programmed to a default value of 0x000.
It is good practice in the manufacturing flow to
configure the device to your desired settings.
TABLE 4-2: DEFAULT FACTORY
SETTINGS SELECTION
4.2.1.4 Special Features
There are 5 non-volatile bits that are not directly
mapped into the address space. These bits control the
following functions:
• EEPROM Write Protect
• WiperLock Technology for Non-Volatile Wiper 0
• WiperLock Technology for Non-Volatile Wiper 1
• WiperLock Technology for Non-Volatile Wiper 2
• WiperLock Technology for Non-Volatile Wiper 3
The operation of WiperLock Technology is discussed in
Section 5.3. The state of the WL0, WL1, WL2, WL3,
and WP bits is reflected in the STATUS register (see
Register 4-1).
EEPROM Write Protect
All internal EEPROM memory can be Write Protected.
When EEPROM memory is Write Protected, Write
commands to the internal EEPROM are prevented.
Write Protect (WP
) can be enabled/disabled by two
methods. These are:
• External WP
Hardware pin (MCP43X1 devices
only)
• Non-Volatile configuration bit (WP)
High Voltage commands are required to enable and
disable the non-volatile WP bit. These commands are
shown in Section 7.9 “Modify Write Protect or
WiperLock Technology (High Voltage)”.
To write to EEPROM, both the external WP
pin and the
internal WP EEPROM bit must be disabled. Write
Protect does not block commands to the volatile
registers.
4.2.2 VOLATILE MEMORY (RAM)
There are seven Volatile Memory locations. These are:
• Volatile Wiper 0
• Volatile Wiper 1
• Volatile Wiper 2
• Volatile Wiper 3
• Status Register
• Terminal Control (TCON0) Register 0
• Terminal Control (TCON)1 Register 1
The volatile memory starts functioning at the RAM
retention voltage (V
RAM
).
Resistance
Code
Typical
R
AB
Value
Default POR
Wiper Setting
Wiper
Code
WiperLock™
Technology and
Write Protect Setting
8-bit 7-bit
-502 5.0 kΩ Mid scale 80h 40h Disabled
-103 10.0 kΩ Mid scale 80h 40h Disabled
-503 50.0 kΩ Mid scale 80h 40h Disabled
-104 100.0 kΩ Mid scale 80h 40h Disabled