National CP3BT26 - Manual (Page 61)

61 www.national.com
CP3
BT26
13.0 Multi-Input Wake-Up
The Multi-Input Wake-Up (MIWU) unit consists of two iden-
tical 16-channel modules. Each module can assert a wake-
up signal for exiting from a low-power mode, and each can
assert an interrupt request on any of four Interrupt Control
Unit (ICU) channels assigned to that module. The modules
operate independently, so each may assert an interrupt re-
quest to the ICU. Together, these modules provide 32 MIWU
input channels and 8 interrupt request outputs.
Each 16-channel module monitors its inputs for a software-
selectable trigger condition. On detection of a trigger condi-
tion, the module generates an interrupt request and if en-
abled, a wake-up request. A wake-up request can be used
by the power management unit to exit the Halt, Idle, or Pow-
er Save mode and return to the Active mode. An interrupt
request generates an interrupt to the CPU, which allows an
interrupt handler to respond to MIWU events.
The wake-up event only activates the clocks and CPU, but
does not by itself initiate execution of any code. It is the in-
terrupt request asserted by the MIWU that gets the CPU to
start executing code, by jumping to the corresponding inter-
rupt handler. Therefore, setting up the MIWU interrupt han-
dler is essential for any wake-up operation.
Each 16-channel module has four interrupt requests that
can be routed to the ICU as shown in Figure 9. Each of the
16 channels can be programmed to activate one of these
four interrupt requests.
The 32 MIWU channels are named WUI0 through WUI31,
as shown in Table 27.
Each channel can be configured to trigger on rising or falling
edges, as determined by the setting in the WK0EDG or
WK1EDG register. Each trigger event is latched into the
WK0PND or WK1PND register. If a trigger event is enabled
by its respective bit in the WK0ENA or WK1ENA register, an
active wake-up/interrupt signal is generated. Software can
determine which channel has generated the active signal by
reading the WK0PND or WK1PND register.
The MIWU is active at all times, including the Halt mode. All
device clocks are stopped in this mode. Therefore, detecting
an external trigger condition and the subsequent setting of
the pending bit are not synchronous to the System Clock.
Figure 9. Multi-Input Wake-Up Module Block Diagram
WK0EDG
WK1EDG WK0PND
WK1PND
WUI16
WUI31
Wake-Up Signal
To Power Mgt
0
15
Peripheral Bus
WK0ICTL1/WK0ICTL2
WK1ICTL1/WK1ICTL2
15 . . . . . . . . . . .
WK0IENA
WK1IENA
0
15 . . . . . . . . . . .
WK0ENA
WK1ENA
0
MIWU Interrupt 3:0
MIWU Interrupt 7:4
Encoder
4
DS218
WUI0
WUI15