ML51/ML54/ML56
Sep. 01, 2020
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ML51/M
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Tec
hnical Reference
Manual
6.7 Self Wake-up Timer (WKT)
6.7.1
Overview
The ML51/ML54/ML56 Series 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 two clock source, internal LIRC 38.4 R/W or LXT
32.768 R/W. 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 16-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 RWK can reloadable when counter is count to overflow. The CWK
can read current count value. 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.
6.7.2
Block Diagram
WKTR
(WKCON.3)
Internal 8-bit Counter
RWK
0
7
WKT
Overflow
Pre-scalar
(1/1~1/2048)
WKPS[2:0]
(WKCON[2:0])
WKTF
(WKCON.4)
WKT Interrupt
38.4 kHz Internal
Oscillator
F
LIRC
WKTCK
(WKCON.5)
CWK
0
7
32 kHz External
Oscillator
0
F
LXT
1
Figure 6.7-1 Self Wake-Up Timer Block Diagram
