BCM4319 Preliminary Data Sheet
Low-Power Shutdown
Each resource is in one of four states: enabled, disabled, transition_on, and transition_off. Each resource has
a timer that contains 0 when the resource is enabled or disabled and a nonzero value in the transition states.
The timer is loaded with the resource's time_on or time_off value when the PMU determines that the resource
must be enabled or disabled, and it decrements on each 32.768 kHz PMU clock. When it reaches 0, the state
changes from transition_off to disabled or transition_on to enabled. If the time_on value is 0, the resource can
go immediately from disabled to enabled. Similarly, a time_off value of 0 indicates that the resource can go
immediately from enabled to disabled. The terms enable sequence and disable sequence refer to either the
immediate transition or the timer load-decrement sequence.
During each clock cycle, the PMU sequencer performs the following:
1. Computes the required resource set based on requests and the resource dependency table.
2. Decrements all timers whose values are nonzero. If a timer reaches 0, the PMU clears the ResourcePending
bit for the resource and inverts the ResourceState bit.
3. Compares the request with the current resource status and determines which resources must be enabled or
disabled.
4. Initiates a disable sequence for each resource that is enabled, no longer being requested, and has no
powered-up dependents.
5. Initiates an enable sequence for each resource that is disabled, is being requested, and has all of its
dependencies enabled.
Low-Power Shutdown
The BCM4319 provides a low-power shutdown feature that allows the device to be turned off while the host and
other system devices remain operational. When the BCM4319 is not needed in the system, WL_REG_ON
should be driven low while VDDIO remains powered. This allows the BCM4319 to be effectively off while
keeping the I/O pins powered, so that they do not draw extra current from any other devices connected to the I/
O.
During a low-power shutdown state, provided VDDIO remains applied to the BCM4319, all outputs are tristated,
and most inputs signals are disabled. Input voltages must remain within the limits defined for normal operation.
This is done to prevent current paths or to create loading on any digital signals in the system, and it enables the
BCM4319 to be fully integrated in an embedded device and to take full advantage of the lowest power saving
modes.
The frequency reference input (XTALIN) is designed to be a high-impedance input that does not load down the
driving signal, even if the chip does not have VDDIO power applied to it.
When the BCM4319 is powered on from this state, it is the same as a normal power-up, and the device does
not contain any information about its state from before it was powered down.
Broadcom®
Single-Chip IEEE 802.11™ a/b/g/n MAC/Baseband/Radio
Page 19
April 2, 2014 • 4319-DS05-R
CYPRESS [ CYPRESS ]
