CAT93C86

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4

Table 8. INSTRUCTION SET

Instruction

Start

Bit

Opcode

Address

Data

Comments

x8

x16

x8

x16

READ

1

10

A10−A0

A9−A0

Read Address AN– A0

ERASE

1

11

A10−A0

A9−A0

Clear Address AN– A0

WRITE

1

01

A10−A0

A9−A0

D7−D0

D15−D0

Write Address AN– A0

EWEN

1

00

11XXXXXXXXX

11XXXXXXXX

Write Enable

EWDS

1

00

00XXXXXXXXX

00XXXXXXXX

Write Disable

ERAL

1

00

10XXXXXXXXX

10XXXXXXXX

Clear All Addresses

WRAL

1

00

01XXXXXXXXX

01XXXXXXXX

D7−D0

D15−D0

Write All Addresses

Device Operation

The CAT93C86 is a 16,384−bit nonvolatile memory

intended for use with industry standard microprocessors.

The CAT93C86 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 CAT93C86 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 CAT93C86 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

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

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 CAT93C86 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.