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MCP23009T Datasheet(PDF) 6 Page - Microchip Technology |
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MCP23009T Datasheet(HTML) 6 Page - Microchip Technology |
6 / 50 page MCP23009/MCP23S09 DS22121B-page 6 © 2009 Microchip Technology Inc. 1.2 Power-on Reset (POR) The on-chip POR circuit holds the device in reset until VDD has reached a high enough voltage to deactivate the POR circuit (i.e., release the device from reset). The maximum VDD rise time is specified in the electrical specification section. When the device exits the POR condition (releases reset), device operating parameters (i.e., voltage, temperature, serial bus frequency, etc.) must be met to ensure proper operation. 1.3 Serial Interface This block handles the functionality of the I2C (MCP23009) or SPI (MCP23S09) interface protocol. The MCP23X09 contains eleven (11) individual registers which can be addressed through the Serial Interface block (Table 1-3). TABLE 1-3: REGISTER ADDRESSES 1.3.1 BYTE MODE AND SEQUENTIAL MODE The MCP23X09 has the ability to operate in “Byte Mode” or “Sequential Mode” (IOCON.SEQOP). Byte mode and sequential mode are not to be confused with I2C byte operations and sequential operations. The modes explained here relate to the device’s internal address pointer and whether or not it is incremented after each byte is clocked on the serial interface. Byte Mode disables automatic address pointer incre- menting. When operating in Byte Mode, the MCP23X09 does not increment its internal address counter after each byte during the data transfer. This gives the ability to continually access the same address by providing extra clocks (without additional control bytes). This is useful for polling the GPIO register for data changes or for continually writing to the output latches. Sequential Mode enables automatic address pointer incrementing. When operating in Sequential Mode, the MCP23X09 increments its address counter after each byte during the data transfer. The address pointer automatically rolls over to address 00h after accessing the last register. These two modes are not to be confused with single writes/reads and continuous writes/reads which are serial protocol sequences. For example, the device may be configured for Byte Mode and the master may perform a continuous read. In this case, the MCP23X09 would not increment the address pointer and would repeatedly drive data from the same location. 1.3.2 I2C INTERFACE 1.3.2.1 I2C Write Operation The I2C write operation includes the control byte and register address sequence, as shown in the bottom of Figure 1-1. This sequence is followed by eight bits of data from the master and an Acknowledge (ACK) from the MCP23009. The operation is ended with a stop (P) or restart (SR) condition being generated by the master. Data is written to the MCP23009 after every byte transfer. If a stop or restart condition is generated during a data transfer, the data will not be written to the MCP23009. Both “byte mode” and “sequential mode” are supported by the MCP23009. If sequential mode is enabled (default), the MCP23009 increments its address counter after each ACK during the data transfer. 1.3.2.2 I2C Read Operation I2C read operations include the control byte sequence, as shown in the bottom of Figure 1-1. This sequence is followed by another control byte (including the Start condition and ACK) with the R/W bit equal to a logic one (R/W = 1). The MCP23009 then transmits the data contained in the addressed register. The sequence is ended with the master generating a Stop or Restart condition. 1.3.2.3 I2C Sequential Write/Read For sequential operations (Write or Read), instead of transmitting a Stop or Restart condition after the data transfer, the master clocks the next byte pointed to by the address pointer (see Section 1.3.1 “Byte Mode and Sequential Mode” for details regarding sequential operation control). The sequence ends with the master sending a Stop or Restart condition. The MCP23009 address pointer will roll over to address zero after reaching the last register address. Refer to Figure 1-1. Address Access to: 00h IODIR 01h IPOL 02h GPINTEN 03h DEFVAL 04h INTCON 05h IOCON 06h GPPU 07h INTF 08h INTCAP (Read-only) 09h GPIO 0Ah OLAT |
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