MEC1404 Datasheet, PDF (237/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
Offset ^04h
Bits
Description
Type
0 OBF
R
The Output Buffer Full bit is set to indicate that a the ACPI_EC has
written a data to the ACPI_OS and that data is ready. This bit is
automatically cleared when all the data has been read by the
ACPI_OS.
Note:
The setting and clearing of this OBF varies depending
on the setting FOUR_BYTE_ACCESS bit in the OS
Byte Control Register. Two scenarios follow:
1. The OBF bit is set if the Four Byte Access bit in the OS Byte
Control Register is ‘0’ when the ACPI_EC writes to the
EC2OS Data EC Byte 0 Register.
The OBF is cleared if the Four Byte Access bit in the OS Byte
Control Register is cleared to ‘0’ when the ACPI_OS reads from
the ACPI OS Data Register Byte 0 Register.
2. The OBF is set if the Four Byte Access bit in the OS Byte
Control Register is set to ‘1’ when the ACPI_EC writes to the
EC2OS Data EC Byte 3 Register.
The OBF is cleared if the Four Byte Access bit in the OS Byte
Control Register is set to ‘1’ when the ACPI_OS reads from the
ACPI OS Data Register Byte 3 Register.
The ACPI Specification usage model is as follows:
1. The ACPI_EC must generate a software interrupt (See
Note: on page 227) to alert the ACPI_OS that the data is
available.
2. The ACPI_OS reads the OS STATUS OS Register and sees
the OBF flag set, the ACPI_OS reads all the data available
in the ACPI-OS DATA BYTES[3:0].
3. The ACPI_OS reads all the data available in the ACPI-OS
DATA BYTES[3:0]. This causes the OBF bit to be automati-
cally cleared by hardware and the associated OBF interrupt
to be asserted.
Default
0h
Reset
Event
nSYSR
ST
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DS00001956D-page 237