900844 datasheet(30/118 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

900844

FUNCTIONAL DEVICE OPERATION

SYSTEM CONTROL INTERFACE

FUNCTIONAL DEVICE OPERATION

SYSTEM CONTROL INTERFACE

OVERVIEW

This section addresses the various interfaces and I/Os between the PMIC solution and the rest of the system.

The system control interface includes the following:

• SPI interface.

• Interrupt controller

• Platform sideband signals

• Special registers

SPI INTERFACE

The 900844 contains a SPI interface port which allows a host controller to access the register set. Using these registers,

900844 resources can be controlled. The registers also provide information on the PMIC status, as well as information on external

signals.

The addressable register map spans 1024 registers of 8 data bits each. The map is not fully populated. A detailed structure

of the register set along with bit names, positions, and basic descriptions, are given in Table 74. Expanded bit descriptions are

included in the individual functional sections for application guidance.

Note that not all bits are truly writable. Refer to the individual sub-circuit descriptions and Table 74 to determine the read/write

capability of each bit.

The System Controller Unit (SCU) within the Platform Controller Hub (PCH) is the master, while the PMIC is the slave. The

SPI interface operates at a typical frequency of 12.5 MHz, and at a maximum frequency of 25 MHz, with lower speeds supported.

The SPI interface is configured in mode 1: clock polarity is active high (CPOL = 0), and data is latched on the falling edge of

the clock (CPHA = 1). The chip select signal, SPICSB, is active low. The SPICSB line must remain active during the entire SPI

transfer. The MISO line will be tri-stated while SPICSB is high.

The SPI frame consists of 24 bits: a Read/Write bit, a 10-bit address code (MSB first), 5 "dead" bits and 8 data bits (also MSB

first). The Read/Write bit selects whether the SPI transaction is a read or a write: for a write operation, the R/W bit must be a one;

for a read operation, it must be a zero.

For a read transaction, any data on the MOSI pin after the address bits is ignored. The MISO pin will output the data field

pointed to by the 10-bit address loaded at the beginning of the SPI sequence. SPI read backs of the address field and unused

bits are returned as zero. For read operations, the PMIC supports address auto-increment.

For a write operation, once all the data bits are written, the data is transferred into the registers on the falling edge of the 24th

clock cycle. All unused SPI bits in each register must be written to a zero.

To start a new SPI transfer, the SPICSB line must go inactive and then active. After the LSB of data is sent, if the SPICSB line

is held low, up to seven additional address/data packets may be sent as writes to the PMIC. Refer to the VRCOMP Pin section.

The following diagrams illustrate the SPI Write Protocol, SPI Read Protocol, and SPI Timing.

Table 5. SPI Interface Pin Functionality

Pin Name

SPI Functionality

SPICLK

SPI Clock Input (up to 25 MHz)

MOSI

Master Out / Slave In (Serial Data In)

MISO

Master In / Slave Out (Serial Data Out)

SPICSB

Chip Select (Active Low)

SPIVCC

SPI Bus Supply - 1.8 V typical

900844 Datasheet(PDF) 30 Page - Freescale Semiconductor, Inc

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