PCA9672: I2C-bus to Parallel Port Expander for LED Control and Remote I/O

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"PCA9672是一款基于I2C总线的并行端口扩展器，具有1MHz的高速I2C总线接口（Fast-mode Plus），适用于2.3V至5.5V的工作电压范围，其I/O引脚耐压5.5V，并在上电时默认为输入状态。设备提供8位远程I/O引脚，具有25mA的拉电流能力，用于低功耗应用，如驱动LED。PCA9672还具备硬件地址输入和复位输入功能，以及独立分配的准双向端口，可以作为输入监测中断状态或键盘，也可作为输出驱动指示设备。系统主控可以通过单个寄存器读取输入端口或写入输出端口。此外，PCA9672拥有两个硬件地址引脚，最多可支持16个相同设备在同一I2C总线上工作，无需总线缓冲器，因此可以支持多达128个I/O，例如128个LED。" PCA9672是一种微控制器扩展芯片，通过两线制双向I2C总线实现与主机通信。它包含8个准双向端口，这些端口在电源启动时默认设置为输入模式，允许系统监控外部设备的状态，如按钮或中断请求。每个端口都有25mA的拉电流驱动能力，这使得PCA9672可以直接驱动LED，而无需额外的驱动电路。这种设计非常适合移动设备，因为它在静态状态下仅消耗2.5μA的典型电流，大大降低了功耗。该芯片支持1MHz的Fast-mode Plus I2C-bus，这种高速接口不仅可用于LED的脉宽调制（PWM）调光，而且由于其高达30mA的驱动能力，可以在不增加总线缓冲器的情况下连接更多的设备，保持总线的稳定性。PCA9672还包括三个硬件地址输入引脚，允许最多16个相同的PCA9672器件连接到同一个I2C总线上，总共能提供128个I/O通道，这在需要大量GPIO扩展的应用中非常有用，比如LED矩阵显示或者复杂的用户界面。 PCA9672的复位输入功能使系统能够对整个扩展器进行同步初始化，确保所有端口按预期工作。通过单个寄存器进行读写操作，系统主控可以轻松地管理和控制所有I/O状态，提高效率和灵活性。PCA9672是一款高效、灵活的I2C总线GPIO扩展器，适用于需要大量GPIO扩展且对功耗和性能有要求的嵌入式系统设计。

Product data sheet Rev. 3 — 27 May 2013 7 of 36

NXP Semiconductors

PCA9672

Remote 8-bit I/O expander for Fm+ I

C-bus with interrupt and reset

7.2.1 Software Reset

The Software Reset Call allows all the devices in the I

C-bus to be reset to the power-up

state value through a specific formatted I

C-bus command. To be performed correctly, it

implies that the I

C-bus is functional and that there is no device hanging the bus.

The Software Reset sequence is defined as following:

1. A START command is sent by the I

C-bus master.

2. The reserved General Call I

C-bus address ‘0000 000’ with the R/W bit set to 0 (write)

is sent by the I

C-bus master.

3. The PCA9672 device(s) acknowledge(s) after seeing the General Call address

‘0000 0000’ (00h) only. If the R/W

bit is set to 1 (read), no acknowledge is returned to

the I

C-bus master.

4. Once the General Call address has been sent and acknowledged, the master sends

1 byte. The value of the byte must be equal to 06h.

a. The PCA9672 acknowledges this value only. If the byte is not equal to 06h, the

PCA9672 does not acknowledge it.

If more than 1 byte of data is sent, the PCA9672 does not acknowledge any more.

5. Once the right byte has been sent and correctly acknowledged, the master sends a

STOP command to end the Software Reset sequence: the PCA9672 then resets to

the default value (power-up value) and is ready to be addressed again within the

specified bus free time. If the master sends a Repeated START instead, no reset is

performed.

The I

C-bus master must interpret a non-acknowledge from the PCA9672 (at any time) as

a ‘Software Reset Abort’. The PCA9672 does not initiate a reset of its registers.

The unique sequence that initiates a Software Reset is described in Figure 9

Simple code for Software Reset:

Fig 9. Software Reset sequence

002aac329

0 0 0 0 0 0 0 AS 0

SWRST Call I

C-bus address

START condition R/W

acknowledge

from slave(s)

0 0 0 0 1 1 00

SWRST data = 06h

acknowledge

from slave(s)

PCA9672 is(are) reset.

Registers are set to default power-up values.

Product data sheet Rev. 3 — 27 May 2013 8 of 36

NXP Semiconductors

PCA9672

Remote 8-bit I/O expander for Fm+ I

C-bus with interrupt and reset

7.2.2 Device ID (PCA9672 ID field)

The Device ID field is a 3-byte read-only (24 bits) word giving the following information:

• 12 bits with the manufacturer name, unique per manufacturer (for example, NXP).

• 9 bits with the part identification, assigned by manufacturer.

• 3 bits with the die revision, assigned by manufacturer (for example, Rev X).

The Device ID is read-only, hardwired in the device and can be accessed as follows:

1. START command

2. The master sends the Reserved Device ID I

C-bus address ‘1111 100’ with the R/W

bit set to 0 (write).

3. The master sends the I

C-bus slave address of the slave device it needs to identify.

The LSB is a ‘Don’t care’ value. Only one device must acknowledge this byte (the one

that has the I

C-bus slave address).

4. The master sends a Re-START command.

Remark: A STOP command followed by a START command will reset the slave state

machine and the Device ID read cannot be performed.

Remark: A STOP command or a Re-START command followed by an access to

another slave device will reset the slave state machine and the Device ID read cannot

be performed.

5. The master sends the Reserved Device ID I

C-bus address ‘1111 100’ with the R/W

bit set to 1 (read).

6. The device ID read can be done, starting with the 12 manufacturer bits (first byte +

4 MSB of the second byte), followed by the 9 part identification bits and then the

3 die revision bits (3 LSB of the third byte).

7. The master ends the reading sequence by NACKing the last byte, thus resetting the

slave device state machine and allowing the master to send the STOP command.

Remark: The reading of the Device ID can be stopped anytime by sending a NACK

command.

Remark: If the master continues to ACK the bytes after the third byte, the PCA9672

rolls back to the first byte and keeps sending the Device ID sequence until a NACK

has been detected.

For the PCA9672, the Device ID is as shown in Figure 10

Fig 10. PCA9672 Device ID field

002aac326

0 0

10 1 0 0 0 0 1

00 0 0 0 0 0 0

revision

0 0 0 0

part identification

manufacturer

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