MS51
Nov. 28, 2019
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MS51
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UAL
6.8 Self Wake-Up Timer (WKT)
6.8.1
Overview
The MS51 has a dedicated Self Wake-up Timer (WKT), which serves for a periodic wake-up timer in
low power mode or for general purpose timer. WKT remains counting in Idle or Power-down mode.
When WKT is being used as a wake-up timer, a start of WKT can occur just prior to entering a power
management mode. WKT has one clock source, internal 10 kHz. Note that the system clock frequency
must be twice over WKT clock. If WKT starts counting, the selected clock source will remain active
once the device enters Idle or Power-down mode. Note that the selected clock source of WKT will not
automatically enabled along with WKT configuration. User should manually enable the selected clock
source and waiting for stability to ensure a proper operation.
The WKT is implemented simply as a 8-bit auto-reload, up-counting timer with pre-scale 1/1 to 1/2048
selected by WKPS[2:0] (WKCON[2:0]). User fills the reload value into RWK register to determine its
overflow rate. The WKTR (WKCON.3) can be set to start counting. When the counter rolls over FFH,
WKTF (WKCON.4) is set as 1 and a reload is generated and causes the contents of the RWK register
to be reloaded into the internal 8-bit counter. If EWKT (EIE1.2) is set as 1, WKT interrupt service
routine will be served.
WKTR
(WKCON.3)
Internal 16-bit Counter
RWK
0
WKT
Overflow
Pre-scalar
(1/1~1/2048)
WKPS[2:0]
(WKCON[2:0])
WKTF
(WKCON.4)
WKT Interrupt
10 kHz Internal
Oscillator
F
LIRC
15
Figure 6.8-1 Self Wake-Up Timer Block Diagram