CAV93C86
http://onsemi.com
4
Device Operation
The CAV93C86 is a 16,384−bit nonvolatile memory
intended for use with industry standard microprocessors.
The CAV93C86 can be organized as either registers of 16
bits or 8 bits. When organized as X16, seven 13−bit
instructions control the reading, writing and erase
operations of the device. When organized as X8, seven
14−bit instructions control the reading, writing and erase
operations of the device. The CAV93C86 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).
Note: The Write, Erase, Write all and Erase all instructions
require PE = 1. If PE is left floating, 93C86 is in Program
Enabled mode. For Write Enable and Write Disable
instruction PE = don’t care.
Read
Upon receiving a READ command and an address
(clocked into the DI pin), the DO pin of the CAV93C86 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
).
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 to 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 CAV93C86 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.
