MEC1322 Datasheet, PDF (138/456 Pages) Microchip Technology – Keyboard and Embedded Controller for Notebook PC

MEC1322
Offset ^04h
Bits
Description
Type
1 IBF
R
The Input Buffer Full bit is set to indicate that a the ACPI_OS has
written a command or data to the ACPI_EC and that data is ready.
This bit is automatically cleared when data has been read by the
ACPI_EC.
Note:
The setting and clearing of this IBF varies depending on
the setting of the following bits: CMD bit in this register
and FOUR_BYTE_ACCESS bit in the OS Byte Control
Register. Three scenarios follow:
1. The IBF is set when the ACPI_OS writes to the ACPI OS
COMMAND Register. This same write autonomously sets the
CMD bit in this register.
The IBF is cleared if the CMD bit in this register is set and the
ACPI_EC reads from the OS2EC Data EC Byte 0 Register.
Note:
When CMD bit in this register is set the FOUR_BYTE_-
ACCESS bit in the OS Byte Control Register has no
impact on the IBF bit behavior.
2. A write by the to the ACPI_OS to the ACPI OS Data Register
Byte 0 Register sets the IBF bit if the FOUR_BYTE_ACCESS
bit in the OS Byte Control Register is in the cleared to ‘0’ state
prior to this write. This same write autonomously clears the
CMD bit in this register.
A read of the OS2EC Data EC Byte 0 Register clears the IBF bit if
the FOUR_BYTE_ACCESS bit in the OS Byte Control Register is in
the cleared to ‘0’ state prior to this read.
3. A write by the to the ACPI_OS to the ACPI OS Data Register
Byte 3 Register sets the IBF bit if the FOUR_BYTE_ACCESS
bit in the OS Byte Control Register is in the set to ‘1’ state prior
to this write. This same write autonomously clears the CMD
bit in this register.
A read of the OS2EC Data EC Byte 3 Register clears the IBF bit if
the FOUR_BYTE_ACCESS bit in the OS Byte Control Register is in
the set to ‘1’ state prior to this read.
An EC_IBF interrupt signals the ACPI_EC that there is data avail-
able. The ACPI Specification usage model is as follows:
1. The ACPI_EC reads the EC STATUS Register and sees the
IBF flag set,
2. The ACPI_EC reads all the data available in the OS2EC
DATA BYTES[3:0]. This causes the IBF bit to be automatically
cleared by hardware.
3. The ACPI_EC must then generate a software interrupt (See
Note: on page 130) to alert the ACPI_OS that the data has
been read and that the host is free to write more data to the
ACPI_EC as needed.
Default
0h
Reset
Event
VCC1_R
ESET
DS00001719D-page 138
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