CAV93C76
http://onsemi.com
4
Device Operation
The CAV93C76 is a 8192−bit nonvolatile memory
intended for use with industry standard microprocessors.
The CAV93C76 can be organized as either registers of 16
bits or 8 bits. When organized as X16, seven 13−bit
instructions control the read, write and erase operations of
the device. When organized as X8, seven 14−bit instructions
control the read, write and erase operations of the device.
The CAV93C76 operates on a single power supply and will
generate on chip, the high voltage required during any write
operation.
Instructions, addresses, and write data are clocked into the
DI pin on the rising edge of the clock (SK). The DO pin is
normally in a high impedance state except when reading data
from the device, or when checking the ready/busy status
after a write operation.
The ready/busy status can be determined after the start of
a write operation by selecting the device (CS high) and
polling the DO pin; DO low indicates that the write
operation is not completed, while DO high indicates that the
device is ready for the next instruction. If necessary, the DO
pin may be placed back into a high impedance state during
chip select by shifting a dummy “1” into the DI pin. The DO
pin will enter the high impedance state on the falling edge of
the clock (SK). Placing the DO pin into the high impedance
state is recommended in applications where the DI pin and
the DO pin are to be tied together to form a common DI/O
pin.
The format for all instructions sent to the device is a
logical “1” start bit, a 2−bit (or 4−bit) opcode, 10−bit address
(an additional bit when organized X8) and for write
operations a 16−bit data field (8−bit for X8 organizations).
The most significant bit of the address is “don’t care” but it
must be present.
Read
Upon receiving a READ command and an address
(clocked into the DI pin), the DO pin of the CAV93C76 will
come out of the high impedance state and, after sending an
initial dummy zero bit, will begin shifting out the data
addressed (MSB first). The output data bits will toggle on
the rising edge of the SK clock and are stable after the
specified time delay (t
PD0
or t
PD1
).
For the CAV93C76, after the initial data word has been
shifted out and CS remains asserted with the SK clock
continuing to toggle, the device will automatically
increment to the next address and shift out the next data word
in a sequential READ mode. As long as CS is continuously
asserted and SK continues to toggle, the device will keep
incrementing to the next address automatically until it
reaches the end of the address space, then loops back to
address 0. In the sequential READ mode, only the initial data
word is preceeded by a dummy zero bit. All subsequent data
words will follow without a dummy zero bit.
Write
After receiving a WRITE command, address and the data,
the CS (Chip Select) pin must be deselected for a minimum
of t
CSMIN
. The falling edge of CS will start the self clocking
clear and data store cycle of the memory location specified
in the instruction. The clocking of the SK pin is not
necessary after the device has entered the self clocking
mode. The ready/busy status of the CAV93C76 can be
determined by selecting the device and polling the DO pin.
Since this device features Auto−Clear before write, it is
NOT necessary to erase a memory location before it is
written into.
SK
DI
CS
DO
VALID
VALID
DATA VALID
Figure 2. Synchronous Data Timing
t
CSS
t
SKHI
t
SKLOW
t
DIS
t
DIS
t
DIH
t
CSH
t
CSMN
t
PD0
, t
PD1
