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ST90158 - TIMER/WATCHDOG (WDT)
TIMER/WATCHDOG (Cont’d)
9.1.5 Register Description
The Timer/Watchdog is associated with 4 registers
mapped into Group F, Page 0 of the Register File.
WDTHR: Timer/Watchdog High Register
WDTLR: Timer/Watchdog Low Register
WDTPR: Timer/Watchdog Prescaler Register
WDTCR: Timer/Watchdog Control Register
Three additional control bits are mapped in the fol-
lowing registers on Page 0:
Watchdog Mode Enable, (WCR.6)
Top Level Interrupt Selection, (EIVR.2)
Interrupt A0 Channel Selection, (EIVR.1)
Note: The registers containing these bits also con-
tain other functions. Only the bits relevant to the
operation of the Timer/Watchdog are shown here.
Counter Register
This 16 bit register (WDTLR, WDTHR) is used to
load the 16 bit counter value. The registers can be
read or written “on the fly”.
TIMER/WATCHDOG HIGH REGISTER (WDTHR)
R248 - Read/Write
Register Page: 0
Reset value: 1111 1111 (FFh)
Bit 7:0 = R[15:8]
Counter Most Significant Bits.
TIMER/WATCHDOG LOW REGISTER (WDTLR)
R249 - Read/Write
Register Page: 0
Reset value: 1111 1111b (FFh)
Bit 7:0 = R[7:0]
Counter Least Significant Bits.
TIMER/WATCHDOG PRESCALER REGISTER
(WDTPR)
R250 - Read/Write
Register Page: 0
Reset value: 1111 1111 (FFh)
Bit 7:0 = PR[7:0]
Prescaler value.
A programmable value from 1 (00h) to 256 (FFh).
Warning: In order to prevent incorrect operation of
the Timer/Watchdog, the prescaler (WDTPR) and
counter (WDTRL, WDTRH) registers must be ini-
tialised before starting the Timer/Watchdog. If this
is not done, counting will start with the reset (un-in-
itialised) values.
WATCHDOG
TIMER
CONTROL REGISTER
(WDTCR)
R251- Read/Write
Register Page: 0
Reset value: 0001 0010 (12h)
Bit 7 = ST_SP:
Start/Stop Bit.
This bit is set and cleared by software.
0: Stop counting
1: Start counting (see Warning above)
Bit 6 = S_C:
Single/Continuous.
This bit is set and cleared by software.
0: Continuous Mode
1: Single Mode
Bit 5:4 = INMD[1:2]:
Input mode selection bits.
These bits select the input mode:
70
R15
R14
R13
R12
R11
R10
R9
R8
70
R7
R6
R5
R4
R3
R2
R1
R0
70
PR7
PR6
PR5
PR4
PR3
PR2
PR1
PR0
70
ST_SP
S_C
INMD1
INMD2
INEN
OUTMD
WROUT
OUTEN
INMD1
INMD2
INPUT MODE
0
Event Counter
0
1
Gated Input (Reset value)
1
0
Triggerable Input
1
Retriggerable Input
9