X80140 Datasheet, PDF (12/18 Pages) Intersil Corporation – Voltage Supervisor/Sequencer Quad Programmable Time Delay with Local/Remote Voltage Monitors

X80140, X80141, X80142, X80143, X80144
Control Registers and Memory
The user addressable internal control, status and memory
components of the X80140 can be split up into three parts:
• Control Register (CR)
• Fault Detection Register (FDR)
• EEPROM array
Registers
The Control Registers and Fault Detection Register are
summarized in Table 4. Changing bits in these registers
change the operation of the device or clear fault conditions.
Reading bits from these registers provides information about
device configuration or fault conditions. Reads and writes
are done through the SMBus serial port.
All of the Control Register bits are nonvolatile (except for the
WEL bit), so they do not change when power is removed.
The values of the Register Block can be read at any time by
performing a random read (see Serial Interface) at the
specific byte address location. Only one byte is read by each
register read operation.
Bits in the registers can be modified by performing a single
byte write operation directly to the address of the register
and only one data byte can change for each register write
operation.
EEPROM Array
The X80140 contains a 2kbit EEPROM memory array. This
array can contain information about manufacturing location
and dates, board configuration, fault conditions, service
history, etc. Access to this memory is through the SMBus
serial port. Read and write operations are similar to those of
the control registers, but a single command can write up to
16 bytes at one time. A single read command can return the
entire contents of the EEPROM memory.
Register and Memory Protection
In order to reduce the possibility of inadvertent changes to
either a control register of the contents of memory, several
protection mechanisms are built into the X80140. These are
a Write Enable Latch, Block Protect bits, a Write Protect
Enable bit and a Write Protect pin.
WEL: Write Enable Latch
A write enable latch (WEL) bit controls write accesses to the
nonvolatile registers and the EEPROM memory array in the
X80140. This bit is a volatile latch that powers up in the LOW
(disabled) state. While the WEL bit is LOW, writes to any
address (registers or memory) will be ignored. The WEL bit
is set by writing a “1” to the WEL bit and zeroes to the other
bits of the control register 0 (CR0). It is important to write
only 00h or 80h to the CR0 register.
Once set, WEL remains set until either it is reset to 0 (by
writing a “0” to the WEL bit and zeroes to the other bits of the
control register) or until the part powers up again.
Note, a write to FDR does not require that WEL=1.
BP1 and BP0: Block Protect Bits
The Block Protect Bits, BP1 and BP0, determines which
blocks of the memory array are write protected. A write to a
protected block of memory is ignored. The block protect bits
will prevent write operations to one of four segments of the
array.
00
01
10
11
PROTECTED ADDRESSES
(SIZE)
None (Default)
C0h - FFh (64 bytes)
80h - FFh (128 bytes)
00h - FFh (256 bytes)
ARRAY LOCK
None (Default)
Upper 1/4
Upper 1/2
All
WPEN: Write Protect Enable
The Write Protect pin and Write Protect Enable bit in the
CR1 register control the Programmable Hardware Write
Protect feature. Hardware Protection is enabled when the
WP pin is HIGH and WPEN bit is HIGH and disabled when
WP pin is LOW or the WPEN bit is LOW. When the chip is
Hardware Write Protected, non-volatile writes to all control
registers (CR1, CR2, and CR) are disabled including BP bits,
the WPEN bit itself, and the blocked sections in the memory
Array. Only the section of the memory array that is not block
protected can be written.
Non Volatile Programming Voltage (V_P)
Nonvolatile writes require that a programming voltage be
applied to the VP for the duration of a nonvolatile write
operation.
WEL
LOW
HIGH
HIGH
HIGH
WP
X
LOW
X
HIGH
WPEN
X
X
LOW
HIGH
TABLE 3. WRITE PROTECT CONDITIONS
MEMORY ARRAY
NOT BLOCK
PROTECTED
MEMORY ARRAY
BLOCK PROTECTED
WRITES TO
CR1, CR2, CR3
Writes Blocked
Writes Blocked
Writes Blocked
Writes Enabled
Writes Blocked
Writes Enabled
Writes Enabled
Writes Blocked
Writes Enabled
Writes Enabled
Writes Blocked
Writes Blocked
PROTECTION
Hardware
Software
Software
Hardware
12
FN8153.0
January 20, 2005