PCF8584 datasheet(9/40 Pages) PHILIPS

9 / 40 page

1997 Oct 21

Philips Semiconductors

Product speciﬁcation

I2C-bus controller

PCF8584

In receiver mode the data from the shift register is copied to the read buffer during the acknowledge phase. Further

reception of data is inhibited (SCL held LOW) until the S0 read buffer is read (see Section 6.8.1.1).

In the transmitter mode data is transmitted to the I2C-bus as soon as it is written to the S0 shift register if the serial I/O is

enabled (ESO = 1).

Remarks:

1. A minimum of 6 clock cycles must elapse between consecutive parallel-bus accesses to the PCF8584 when the

I2C-bus controller operates at 8 or 12 MHz. This may be reduced to 3 clock cycles for lower operating frequencies.

2. To start a read operation immediately after a write, it is necessary to read the S0 read buffer in order to invoke

reception of the first byte (‘dummy read’ of the address). Immediately after the acknowledgement, this first byte will

be transferred from the shift register to the read buffer. The next read will then transfer the correct value of the first

byte to the microcontroller bus (see Fig.7).

6.8

Control/status register S1

signal on register select input A0. For more efficient communication between microcontroller/processor and the I2C-bus,

register S1 has separate read and write functions for all bit positions (see Fig.3). The write-only section provides register

access control and control over I2C-bus signals, while the read-only section provides I2C-bus status information.

Table 4

Control/status register S1

Notes

1. For further information see Section 6.8.1.

2. For further information see Section 6.8.2.

3. Logic 1 if not-initialized.

CONTROL/STATUS

BITS

MODE

Control(1)

ESO

ES1

ES2

ENI

STA

STO

ACK

write only

Status(2)

0(3)

STS

BER

AD0/LRB

AAS

LAB

read only

Fig.4 Data shift register/bus buffer S0.

andbook, full pagewidth

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

Read Buffer

Data Shift Register S0 and Read Buffer

Shift register

Read

only

Write

only

to/from

I2C-Bus SDA line

to/from microcontroller parallel bus

MBE705

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