Preliminary

CAT33C804A

6

Doc. No. 25044-00 2/98

CLK

The System Clock is a TTL compatible input pin that

allows operation of the device at a specified frequency.

The CAT33C804A is designed with an internal divider to

produce a 9600 baud output for an input clock frequency

of 4.9152 MHz.

DI

The Data Input pin is TTL compatible and accepts data

and instructions in a serial format. Each byte must begin

with “0” as a start bit. The device will accept as many

bytes as an instruction requires, including both data and

address bytes. Extra bits will be disregarded if they are

“1”s and extra “0”s will be misinterpreted as the start bit

of the next instruction. An instruction error will cause the

device to abort operation and all I/O communication will

be terminated until a reset is received.

DO

The Data Output pin is a tri-state TTL compatible output.

It is normally in a high impedance state unless a READ

or an ENABLE BUSY instruction is executed. Following

the completion of a 16-bit or 8-bit data stream, the output

will return to the high impedance state. During a pro-

gram/erase cycle, if the ENABLE BUSY instruction has

been previously executed, the output will stay LOW

while the device is BUSY, and it will be set HIGH when

the program/erase cycle is completed. DO will stay

HIGH until the completion of the next instruction’s op-

code and, if the next instruction is a READ, DO will output

the appropriate data at the end of the instruction. If the

ENABLE BUSY instruction has not been previously

executed, DO will stay in a high impedance state. DO will

CS

DI

HIGH-Z

DO

OP0–OP7

tEW

BUSY(1)

OP CODE

A8–A15

ADDRESS

A0–A7

ADDRESS

D0–D7

DATA

Figure 5. Program/Erase Timing (x16 Format)

Figure 4. Program/Erase Timing (x8 Format)

33C804 F07

CS

DI

HIGH-Z

DO

OP0–OP7

tEW

BUSY(1)

OP CODE

A0–A7

ADDRESS

D8–D15

DATA

D0–D7

DATA

33C804 F08

Note:

(1) DO becomes low to indicate busy status if ENBSY was previously executed. If ENBSY was not previously executed, DO will be in the

High-Z condition.