Zilog Z8PE002 - Manual (Page 23)

Z8PE002
ZiLOG Z8Plus OTP Microcontroller
DS008700-Z8X0799 P R E L I M I N A R Y 23
STOP MODE OPERATION
The STOP mode provides the lowest possible device stand-
by current. This instruction turns off the on-chip oscillator
and internal system clock.
To enter the STOP mode, the Z8Plus only requires a STOP
instruction. It is not necessary to execute a NOP instruction
immediately before the STOP instruction.
The STOP mode is exited by any one of the following resets:
POR or a Stop-Mode Recovery source. At reset generation,
the processor always restarts the application program at ad-
dress
0020H , and the STOP mode flag is set. Reading the
STOP mode flag does not clear it. The user must clear the
STOP mode flag with software.
Note: Failure to clear the STOP mode flag can result in unde-
fined behavior.
The Z8Plus provides a dedicated Stop-Mode Recovery
(
SMR ) circuit. In this case, a low-level applied to input pin
PB0 (I/O Port B, bit 0) triggers an SMR . To use this mode,
pin PB0 must be configured as an input and the special func-
tion selected before the STOP mode is entered. The Low
level on PB0 must be held for a minimum pulse width
T
WSM
. Program execution starts at address 20h , after the
POR delay.
Notes: 1. The PB0 input, when used for Stop-Mode Recovery,
does not initialize the control registers.
The STOP mode current ( I
CC2
) is minimized when:
• V
CC
is at the low end of the device’s operating range
• Output current sourcing is minimized
• All inputs (digital and analog) are at the Low or High
rail voltages
2. For detailed information about flag settings, see the
Z8Plus User’s Manual .
6F STOP ;enter STOP mode