ez80f92 ZiLOG Semiconductor, ez80f92 Datasheet - Page 43

• Manufacturer Part Number: ez80f92
• Description: Ez80acclaim Flash Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS015313-0508
HALT Mode
Clock Peripheral Power-Down Registers
Caution:
Execution of the CPU’s HALT instruction places the eZ80F92 device into HALT mode.
In HALT mode, the operating characteristics are:
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The CPU can be brought out of HALT mode by any of the following operations:
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To minimize current in HALT mode, the system clock should be disabled for all unused
on-chip peripherals via the Clock Peripheral Power-Down Registers.
To reduce power, the Clock Peripheral Power-Down Registers allow the system clock to
be disabled unused on-chip peripherals. Upon RESET, all peripherals are enabled.
The clock to unused peripherals can be disabled by setting the appropriate bit in the Clock
Peripheral Power-Down Registers to 1. When powered down, the peripherals are com-
pletely disabled. To re-enable, the bit in the Clock Peripheral Power-Down Registers must
be cleared to 0.
Many peripherals feature separate enable/disable control bits that must be appropriately
set for operation. These peripheral specific enable/disable bits do not provide the same
level of power reduction as the Clock Peripheral Power-Down Registers. When powered
down, the standard peripheral control registers are not accessible for Read or Write access.
See
Primary crystal oscillator is enabled and continues to operate
The system clock is enabled and continues to operate
The CPU is idle
The Program Counter (PC) stops incrementing
A nonmaskable interrupt (NMI)
A maskable interrupt
A RESET via the external RESET pin driven Low
A Watchdog Timer time-out (if configured to generate either an NMI or RESET upon
time-out)
A RESET via execution of a Debug RESET command
Table 4
During HALT mode, the CPU freezes the last address and drives the address bus
with this value. The GPIO Ports remain as configured by the user. Prior to
entering HALT mode, the data bus is driven Low and the control signals MREQ,
CS3:0, INSTRD, BUSACK, IOREQ, RD, and WR are driven High.
and
Table 5
on pages 37 and 38.
Product Specification
Low-Power Modes
36