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Z86C34/C35/C36/C44/C45/C46
CMOS Z8 MCUs with ASCI UART
ZiLOG
DS007601-Z8X0499
P R E L I M I N A R Y
41
Stop-Mode Recovery Register 2 (SMR2).
This register
contains additional Stop-Mode Recovery sources. When
the Stop-Mode Recovery sources are selected in this reg-
ister then
SMR
Register. Bits
D2
,
D3
, and
D4
must be
0
.
Watch-Dog Timer Mode Register (WDTMR).
The
WDT
is a retriggerable one-shot timer that resets the Z8 if it reach-
es its terminal count. The
WDT
is initially enabled by exe-
cuting the
WDT
instruction and refreshed on subsequent ex-
ecutions of the
WDT
instruction. The
WDT
circuit is driven
by an onboard
RC
oscillator or external oscillator from the
XTAL1
pin. The
POR
clock source is selected with bit
4
of
the
WDT
register (Figure 29).
WDT
instruction affects the Z (Zero), S (Sign), and V (Over-
flow) flags. The
WDTMR
must be written to within 64 in-
ternal system clocks. After that, the
WDTMR
is
WRITE
-pro-
tected.
Note:
WDT
time-out while in
STOP
mode does not reset
SMR
,
PCON
,
WDTMR
,
P2M
,
P3M
, Ports 2 & 3 Data Registers,
but the
POR
delay counter is still enabled even though
the
SMR
stop delay is disabled.
WDT Time Select. (D0,D1).
Selects the
WDT
time period
and is configured as indicated in Table 15.
Table 14. Stop-Mode Recovery Source
SMR:10
D1 D0
Operation
Description of Action
0
0
1
0
1
0
POR and/or external reset recovery
Logical AND of P20 through P23
Logical AND of P20 through P27
Figure 29. Watch-Dog Timer Mode Register (WRITE ONLY)
D7
D6
D5
D4
D3
D2
D1
D0
WDTMR (F) 0F
WDT TAP INT RC OSC External Clock
00 3.5 ms 128 TpC
01
*
7 ms 256 TpC
10 14 ms 512 TpC
11 56 ms 2048 TpC
WDT During HALT
0 OFF
1 ON
*
WDT During STOP
0 OFF
1 ON
*
XTAL1/INT RC Select for WDT
0 On-Board RC
*
1 XTAL
Reserved (must be 0)
*
Default setting after RESET
Table 15. WDT Time Select
D1
D0
Timeout of
Internal RC OSC
Timeout of
System Clock
0
0
1
1
0
1
0
1
3.5 ms min
7 ms min
14 ms min
56 ms min
128 SCLK
256 SCLK
512 SCLK
2048 SCLK
Notes:
SCLK = system bus clock cycle.
The default on RESET is 7 ms.
Values provided are for V
CC
= 5.0V.