HT27LC020

Rev. 1.50

5

December 8, 2003

Functional Description

Operation Mode

All the operation modes are shown in the table following.

Mode

CE

OE

PGM

A0

A1

A9

VPP

Output

Read

X (2)

X

X

X

Dout

Output Disable

XX

X

X

High Z

Standby (TTL)

XX

X

X

X

High Z

Standby (CMOS)

±0.3V

XX

X

X

X

High Z

Program

XX

X

Program Verify

XX

X

Product Inhibit

XX

X

X

X

High Z

Manufacturer Code (3)

1C

Device Code (3)

02

±0.5V

Programming of the HT27LC020

When the HT27LC020 is delivered, the chip has all

2048K bits in the

²ONE², or HIGH state. ²ZEROs² are

loaded into the HT27LC020 through programming.

The programming mode is entered when 12.5

±0.2V is ap-

plied with 8 bits in parallel to the data pins.

The programming flowchart in Figure 3 shows the fast

interactive programming algorithm. The interactive al-

gorithm reduces programming time by using 30

msto

105

ms programming pulses and giving each address

only as many pulses as is necessary in order to reliably

program the data. After each pulse is applied to a given

address, the data in that address is verified. If the data

is not verified, additional pulses are given until it is veri-

fied or until the maximum number of pulses is reached

while sequencing through each address of the

HT27LC020. This process is repeated while sequenc-

ing through each address of the HT27LC020. This part

assure that each EPROM bit is programmed to a suffi-

ciently high threshold voltage. This ensures that all bits

have sufficient margin. After the final address is com-

pleted, the entire EPROM memory is read at

±0.3V to verify the entire memory.

Program inhibit Mode

Programming of multiple HT27LC020 in parallel with dif-

ferent data is also easily accomplished by using the Pro-

gram Inhibit Mode. Except for CE, all like inputs of the

parallel HT27LC020 may be common. A TTL low-level pro-

12.5

±0.2V, PGM Low, and OE High will program that

HT27LC020. A high-level CE input inhibits the HT27LC020

from being programmed.

Program Verify Mode

Verification should be performed on the programmed

bits to determine whether they were correctly pro-

grammed. The verification should be performed with

ming voltage.

Auto Product Identification

The Auto Product Identification mode allows the read-

ing out of a binary code from an EPROM that will identify

its manufacturer and the type. This mode is intended for

programming to automatically match the device to be

programmed with its corresponding programming algo-

rithm. This mode is functional in the 25

°C±5°C ambient

temperature range that is required when programming

the HT27LC020.

To activate this mode, the programming equipment must

force 12.0

±0.5V on the address line A9 of the

HT27LC020. Two identifier bytes may then be sequenced

from the device outputs by toggling address line A0 from

these two identifier bytes are given in the Mode Select

Table. All identifiers for the manufacturer and device

codes will possess odd parity, with the MSB (DQ7) de-

will read out the binary code of 7F, continuation code, to

signify the unavailability of manufacturer ID codes.