Z86L88 Datasheet, PDF (52/66 Pages) Zilog, Inc. – INFRARED REMOTE CONTROLLERS

Z86L88/81/86/87/89/73
IR/Low-Voltage Microcontroller
Watch-Dog Timer Mode Register (WDTMR). The WDT
is a retriggerable one-shot timer that resets the Z8 if it
reaches its terminal count. The WDT must initially be en-
abled by executing the WDT instruction and refreshed on
subsequent executions of the WDT instruction. The WDT
circuit is driven by an on-board RC oscillator or external
oscillator from the XTAL1 pin. The WDT instruction affects
the Zero (Z), Sign (S), and Overflow (V) flags.
The POR clock source is selected with bit 4 of the WDT
register. Bit 0 and 1 control a tap circuit that determines the
time-out period. Bit 2 determines whether the WDT is ac-
tive during HALT and Bit 3 determines WDT activity during
STOP. Bits 5 through 7 are reserved (Figure 42). This reg-
ister is accessible only during the first 61 processor cycles
(122 XTAL clocks) from the execution of the first instruc-
tion after Power-On-Reset, Watch-Dog Reset, or a Stop-
Mode Recovery (Figure 43). After this point, the register
cannot be modified by any means, intentional or other-
wise. The WDTMR cannot be read and is located in Bank
F of the Expanded Register Group at address location
0FH. It is organized as follows:
WDTMR (0F) 0F
D7 D6 D5 D4 D3 D2 D1 D0
* Default Setting After Reset
WDT TAP
00
01 *
10
11
INT RC OSC
5 ms
10 ms
20 ms
80 ms
External Clock
256 TpC
512 TpC
1024 TpC
4096 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)
Figure 43. Watch-Dog Timer Mode Register
(Write Only)
52
PRELIMINARY
DS96LV00800