Rainbow Electronics DS4520 User Manual

Page 7

DS4520

9-Bit I

C Nonvolatile

I/O Expander Plus Memory

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*THE SLAVE ADDRESS IS DETERMINED BY
ADDRESS PINS A0, A1, AND A2.

MSB

SLAVE

ADDRESS*

READ/WRITE

BIT

LSB

R/W

Figure 1. DS4520 Slave Address Byte

Table 1. DS4520 Memory Map

ADDRESS

TYPE

NAME

FUNCTION

FACTORY

DEFAULT

00h to 3Fh

EEPROM

User Memory 64 bytes of general-purpose user EEPROM.

00h

40 to E7h

—

Reserved

Undefined address space for future expansion. Reads and writes to this
space have no effect on the device.

—

E8 to EFh

EEPROM

Reserved

—

F0h

Pullup

Enable 0

Pullup enable for I/O_0 to I/O_7. I/O_0 is the LSB and I/O_7 is the MSB. Set
the corresponding bit to enable the pullup; clear the bit to disable the pullup.

00h

F1h

Pullup

Enable 1

Pullup enable for I/O_8. I/O_8 is the LSB. Only the LSB is used. Set the LSB
bit to enable the pullup on I/O_8; clear the LSB to disable the pullup.

00h

F2h

I/O Control 0

I/O control for I/O_0 to I/O_7. I/O_0 is the LSB and I/O_7 is the MSB. Clearing
the corresponding bit of the register pulls the selected I/O pin low; setting the
bit places the pulldown transistor into a high-impedance state. When the
pulldown is high impedance, the output floats if no pullup/down is connected
to the pin.

FFh

F3h

I/O Control 1

I/O control for I/O_8. I/O_8 is the LSB. Only the LSB is used. Clearing the LSB
of the register pulls the I/O_8 pin low; setting the LSB places the pulldown
transistor into a high-impedance state. When the pulldown is high impedance,
the output floats if no pullup/down is connected to the pin.

01h

F4h

Configuration

Configuration register. The LSB is the SEE bit. When set, this bit disables
writes to the EEPROM; writing only affects the shadow SRAM. When set to 0,
both the EEPROM and the shadow SRAM is written.

00h

F5h to F7h

SRAM

Shadowed

EEPROM

[EEPROM

writes are

disabled if

the SEE

bit = 1]

User Memory 3 bytes of general-purpose user EEPROM.

00h

F8h

I/O Status 0

I/O status for I/O_0 to I/O_7. I/O_0 is the LSB and I/O_7 is the MSB. Writing to
this register has no effect. Read this register to determine the state of the
I/O_0 to I/O_7 pins.

F9h

I/O Status 1

I/O status for I/O_8. I/O_8 is the LSB. Only the LSB is used; the other bits
could be any value when read. Writing to this register has no effect. Read this
register to determine the state of the I/O_8 pin.

FAh to FFh

SRAM

SRAM User

6 bytes of general-purpose SRAM.

—