SCS152

DS40150B-page 4

Preliminary

© 1997 Microchip Technology Inc.

2.5

CFG Field

The CFG field is further divided into four subfields:

With ‘PC0 = 0’ and ‘PC1 = 1’, the device is in issuer

mode; with ‘PC0 = 1’ and ‘PC1 = 0’, the device is in user

mode. Some commands can only be used in issuer

mode.

2.6

USER0 Field

The user area can be reprogrammed to any state by the

user in user mode. It also can be locked using the

LOCK0 bit. In issuer mode, this field typically contains

the packaging status of the device. In user mode, this

field can be used for application dependent data.

2.7

UKEY0 Field

In issuer mode, this field contains the transport code; in

user mode, the UKEY0 field contains the key used in

the

signature

function.

The

transport

code

is

programmed during wafer probe and is completely

reprogrammed during personalization to the value of

the key.

3.0

COMMAND INTERFACE

The SCS152 accepts the following basic commands:

RESET, RDBIT/PUTBIT, BITPROG and ERASE. The

extended commands are DECR-ERASE and initiate

signature function.

The device interprets five different SCI/SCK sequences

for all its commands:

a)

An overlap of SCI and SCK for RESET

b)

A single pulse on SCK for RDBIT or PUTBIT

c)

A single pulse on SCI followed by a pulse on

SCK for BITPROG

d)

A repeat of c) for ERASE

e)

A double pulse on SCI followed by a pulse on

SCK for extended commands

Normally, any one of these sequences can be followed

by another; however, once the signature function has

been started, a fixed sequence of commands must fol-

low.

The extended functions are accessed by double pulse

on SCI in the correct address range. Depending on the

current address, the same sequence of events on SCI

and SCK will perform different functions.

Name

Address

Description

PC0

104

First bit of the issuer mode/user

mode indicator

PC1

105

Second bit of the issuer mode/

user mode indicator

N.U.

106

Unused

LOCK0

107

Unlocked status of USER0 area

in user mode: ‘0’ means locked

TABLE 3-1:

EXTENDED FUNCTIONS

Field

Extended Function Accessed by

Double SCI Pulse

CID

Test modes

SER

BITPROG

D4…D0

DECR-ERASE

CFG

Test modes

USER0

BITPROG

UKEY0

Address 163: test mode

Address 259: Initiate signature operation

Other addresses perform BITPROG