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X1226V8IZ View Datasheet(PDF) - Intersil

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X1226V8IZ
Intersil
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X1226V8IZ Datasheet PDF : 25 Pages
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X1226
WEL: Write Enable Latch—Volatile
The WEL bit controls the access to the CCR and mem-
ory array during a write operation. This bit is a volatile
latch that powers up in the LOW (disabled) state. While
the WEL bit is LOW, writes to the CCR or any array
address will be ignored (no acknowledge will be issued
after the Data Byte). The WEL bit is set by writing a “1”
to the WEL bit and zeroes to the other bits of the Status
Register. Once set, WEL remains set until either reset
to 0 (by writing a “0” to the WEL bit and zeroes to the
other bits of the Status Register) or until the part powers
up again. Writes to WEL bit do not cause a nonvolatile
write cycle, so the device is ready for the next operation
immediately after the stop condition.
RTCF: Real Time Clock Fail Bit—Volatile
This bit is set to a “1” after a total power failure. This is
a read only bit that is set by hardware (X1226 inter-
nally) when the device powers up after having lost all
power to the device (both VCC and VBACK go to 0V).
The bit is set regardless of whether VCC or VBACK is
applied first. The loss of only one of the supplies does
not set the RTCF bit to “1”. On power-up after a total
power failure, all registers are set to their default
states and the clock will not increment until at least
one byte is written to the clock register. The first valid
write to the RTC section after a complete power failure
resets the RTCF bit to “0” (writing one byte is suffi-
cient).
Unused Bits:
This device does not use bits 3 or 4 in the SR, but
must have a zero in these bit positions. The Data Byte
output during a SR read will contain zeros in these bit
locations.
CONTROL REGISTERS
The Control Bits and Registers, described under this
section, are nonvolatile.
Block Protect Bits—BP2, BP1, BP0
The Block Protect Bits, BP2, BP1 and BP0, determine
which blocks of the 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 eight segments
of the array. The partitions are described in Table 3.
INTERRUPT CONTROL AND FREQUENCY
OUTPUT REGISTER (INT)
Interrupt Control and Status Bits (IM, AL1E, AL0E)
There are two Interrupt Control bits, Alarm 1 Interrupt
Enable (AL1E) and Alarm 0 Interrupt Enable (AL0E) to
specifically enable or disable the alarm interrupt signal
output (IRQ). The interrupts are enabled when either the
AL1E and AL0E bits are set to ‘1’, respectively.
Table 3. Block Protect Bits
Protected
Addresses
X1226
000
001
None
6000h – 7FFFh
0 1 0 4000h – 7FFFh
011
100
0000h – 7FFFh
0000h – 007Fh
1 0 1 0000h – 00FFh
110
111
0000h – 01FFh
0000h – 03FFh
Array Lock
None
Upper 1/4
Upper 1/2
Full Array
First Page
First 2 pgs
First 4 pgs
First 8 Pgs
Two volatile bits (AL1 and AL0), associated with the two
alarms respectively, indicate if an alarm has happened.
These bits are set on an alarm condition regardless of
whether the IRQ interrupt is enabled. The AL1 and AL0
bits in the status register are reset by the falling edge of
the eighth clock of a read of the register containing the
bits.
Pulse Interrupt Mode
The pulsed interrrupt mode allows for repetitive or
recurring alarm functionality. Hence an repetitive or
recurring alarm can be set for every nth second, or nth
minute, or nth hour, or nth date, or for the same day of
the week. The pulsed interrupt mode can be consid-
ered a repetitive interrupt mode, with the repetition
rate set by the time setting fo the alarm.
The Pulse Interrupt Mode is enabled when the IM bit is
set.
IM Bit
0
1
Interrupt/Alarm Frequency
Single Time Event Set By Alarm
Repetitive/Recurring Time Event Set By
Alarm
The Alarm IRQ output will output a single pulse of
short duration (approximately 10-40ms) once the
alarm condition is met. If the interrupt mode bit (IM bit)
is set, then this pulse will be periodic.
8
FN8098.3
May 8, 2006
 

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