Z8018233FSC datasheet(45/109 Pages) ZILOG

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Z80182/Z8L182

ZILOG INTELLIGENT PERIPHERAL

PRELIMINARY

Zilog

DS971820600

ADDITIONAL FEATURES ON THE Z182 MPU

The following is a detailed description of the enhancements

to the Z8S180 from the standard Z80180 in the areas of

STANDBY, IDLE, and STANDBY-QUICK RECOVERY

modes.

Add-On Features

There are five different power-down modes. SLEEP and

SYSTEM STOP are inherited from the Z80180. In SLEEP

mode, the CPU is in a stopped state while the on-chip

I/Os are still operating. In I/O STOP mode, the on-chip I/Os

are in a stopped state while leaving the CPU running. In

SYSTEM STOP mode, both the CPU and the on-chip I/Os

are in the stopped state to reduce the current consumption.

The Z8S180 has added two additional power-down modes,

STANDBY and IDLE, to reduce the current consumption

even further. The differences among these power-down

modes are summarized in Table 10.

Table 10. Power Down Modes

Power-Down

CPU

On-Chip

Recovery

Recovery Time

Modes

Core

I/O

OSC.

CLKOUT

Source

(Minimum)

SLEEP

Stop

Running

RESET, Interrupts

1.5 Clock

I/O STOP

Running

Stop

Running

By Programming

SYSTEM STOP

Stop

Running

RESET, Interrupts

1.5 Clock

IDLE†

Stop

Running

Stop

RESET, Interrupts, BUSREQ

8 +1.5 Clock

STANDBY†

Stop

RESET, Interrupts, BUSREQ

217 +1.5 Clock (Normal Recovery)

26 +1.5 Clock (Quick Recovery)

Notes:

† IDLE and STANDBY modes are only offered in Z8S180. Note that the

minimum recovery time can be achieved if INTERRUPT is used as the

Recovery Source.

STANDBY Mode

The Z8S180 has been designed to save power. Two low-

power programmable power-down modes have been

added; STANDBY mode and IDLE mode. The

STANDBY/IDLE mode is selected by multiplexing D6 and

D3 of the CPU Control Register (CCR, I/O Address = 1FH).

To enter STANDBY mode:

1. Set D6 and D3 to 1 and 0, respectively.

2. Set the I/O STOP bit (D5 of ICR,

I/O Address = 3FH) to 1.

3. Execute the SLEEP instruction.

When the part is in STANDBY mode, it behaves similar to

the SYSTEM STOP mode which currently exists on the

Z80180, except that the STANDBY mode stops the external

oscillator, internal clocks and reduces power consumption

to typically 50

µA..

Since the clock oscillator has been stopped, a restart of

the oscillator requires a period of time for stabilization. An

18-bit counter has been added in the Z8S180 to allow for

oscillator stabilization. When the part receives an external

IRQ or BUSREQ during STANDBY mode, the oscillator is

restarted and the timer counts down 217 counts before

acknowledgment is sent to the interrupt source.

The recovery source needs to remain asserted for duration

of the 217 count, otherwise standby will be resumed.

The following is a description of how the part exits STANDBY

for different interrupts and modes of operation.

STANDBY Mode Exit with /RESET

The /RESET input needs to be asserted for a duration long

enough for the crystal oscillator to stabilize and then exit

from the STANDBY mode. When /RESET is de-asserted, it

goes through the normal reset timing to start instruction

execution at address (logical and physical) 0000H.

The clocking is resumed within the Z8S180 and at the

system clock output after /RESET is asserted when the

crystal oscillator is restarted, but not yet stabilized.

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