Legacy-Free Keyboard/Embedded Controller with SPI and LPC Docking Interface
Chapter 6 Auto Power Management
Auto Power Management (APM) capabilities are provided for the UART logical device. For each logical
device, two types of power management are provided; direct powerdown and auto powerdown.
6.1
6.2
System Power Management
See the Chapter 12, 8051 System Power Management for details.
UART Power Management
Direct power management is controlled by CR22. Refer to CR22 in the configuration section for more
information.
Auto power management is enabled by CR23 bit 4 and bit 5. When set, these bits allow the following
auto power management operations:
1. The transmitter enters auto powerdown when the transmit buffer and shift register are empty.
2. The receiver enters powerdown when the following conditions are all met:
a. Receive FIFO is empty
b. The receiver is waiting for a start bit
Note: While in powerdown the Ring Indicator interrupt is still valid.
6.3
Exit Auto Power-Down
The transmitter exits powerdown on a write to the transmit buffer. The receiver exits auto powerdown
when RXD changes state.
SMSC LPC47N350
Revision 1.1 (01-14-03)
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