© 1995 Microchip Technology Inc.

DS11182C-page 7

85C72/82/92

9.0

PIN DESCRIPTION

9.1

A0, A1 and A2 Chip Address Inputs

The levels on these inputs are compared with the cor-

responding bits in the slave address.

The chip is

selected if the compare is true. For 85C92, A0 is no

function.

Up to eight 85C72/82s or four 85C92s can be con-

nected to the bus.

9.2

SDA Serial Address/Data Input/Output

This is a bidirectional pin used to transfer addresses

and data into and data out of the device. It is an open

drain terminal, therefore the SDA bus requires a pullup

fer SDA is allowed to change only during SCL LOW.

Changes during SCL HIGH are reserved for indicating

the START and STOP conditions.

9.3

SCL Serial Clock

This input is used to synchronize the data transfer from

and to the device.

9.4

NC No Connect

This pin can be left open or used as a tie point.

Note 1: A “page” is defined as the maximum num-

ber of bytes that can be programmed in a

single write cycle. The 85C72/82 page is

2 bytes long and the 85C92 page is 8

bytes long.

Note 2: A “block” is defined as a continuous area

of memory with distinct boundaries. The

address pointer can not cross the bound-

ary from one block to another. It will, how-

ever, wrap around from the end of a block

to the first location in the same block. The

85C72/82 has only one block (256 bytes),

while the 85C92 has two blocks of 256

bytes each.