Z86D990 Datasheet, PDF (30/102 Pages) Zilog, Inc. – Low-Voltage Micro controllers with ADC

Z86D990/Z86D991 OTP and Z86L99X ROM
Low-Voltage Microcontrollers with ADC
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instruction pipeline by executing a NOP (Op Code = FFh) immediately before the
appropriate sleep instruction. For example:
Mnemonic Comment
Op Code
NOP
; clear the pipeline FFh
STOP
; enter STOP mode 6Fh
or
Mnemonic Comment
NOP
; clear the pipeline
HALT
; enter HALT mode
Op Code
FFh
7Fh
HALT
HALT mode suspends instruction execution and turns off the internal CPU clock
(SCLK). The on-chip oscillator circuit remains active, so the internal Timer clock
(TCLK) continues to run and is applied to the counter/timers and interrupt logic.
An interrupt request, either internally or externally generated, must be executed
(enabled) to exit HALT mode. After the interrupt service routine, the program con-
tinues from the instruction immediately following the HALT.
The HALT mode can also be exited by a POR. In this case, the program execution
restarts at the reset address 000Ch.
STOP
STOP mode provides the lowest possible device standby current. This instruction
turns off both the internal CPU clock (SCLK) and internal Timer clock (TCLK) and
reduces the standby current to the minimum.
The STOP mode is terminated by a POR or SMR source. Terminating the STOP
mode causes the processor to restart the application program at address 000Ch.
Note: When the STOP instruction is executed, the microcontroller goes into the
STOP mode despite any state/change of the state of the port. The ports
need to be checked immediately before the NOP and STOP instructions to
ensure the right input logic before waiting for the change of the ports.
Stop Mode Recovery Sources
Exiting STOP mode using an SMR source is greatly simplified in the Z86D99/
Z86L99 family. The Z86D99/Z86L99 family of products allows 16 individual I/O
PS003807-1002
PRELIMINARY