鈩?/div>
significantly im-
proves on the previous Z80180 models while still providing
full backward compatibility with existing Zilog Z80 devices.
The Z80180/Z8S180/Z8L180 now offers faster execution
speeds, power saving modes, and EMI noise reduction.
This enhanced Z180 design also incorporates additional
feature enhancements to the ASCIs, DMAs, and I
cc
STANDBY Mode power consumption. With the addition of
鈥淓SCC-like鈥?Baud Rate Generators (BRGs), the two ASCIs
now have the flexibility and capability to transfer data asyn-
chronously at rates of up to 512 Kbps. In addition, the ASCI
receiver has added a 4-byte First In First Out (FIFO) which
can be used to buffer incoming data to reduce the inci-
dence of overrun errors. The DMAs have been modified to
allow for a 鈥渃hain-linking鈥?of the two DMA channels when
set to take their DMA requests from the same peripherals
device. This feature allows for non-stop DMA operation be-
tween the two DMA channels, reducing the amount of CPU
intervention (Figure 1).
Not only does the Z80180/Z8S180/Z8L180 consume less
power during normal operations than the previous model,
it has also been designed with three modes intended to fur-
ther reduce the power consumption. Zilog reduced I
cc
pow-
er consumption during STANDBY Mode to a minimum of
10
碌
A by stopping the external oscillators and internal
clock. The SLEEP mode reduces power by placing the
CPU into a 鈥渟topped鈥?state, thereby consuming less cur-
rent while the on-chip I/O device is still operating. The
SYSTEM STOP mode places both the CPU and the on-
chip peripherals into a 鈥渟topped鈥?mode, thereby reducing
power consumption even further.
A new clock doubler feature has been implemented in the
Z80180/Z8S180/Z8L180 device that allows the program-
mer to double the internal clock from that of the external
clock. This provides a systems cost savings by allowing
the use of lower cost, lower frequency crystals instead of
the higher cost, and higher speed oscillators.
The Enhanced Z180 is housed in 80-pin QFP, 68-pin
PLCC, and 64-pin DIP packages.
DS971800401
PRELIMINARY
1-1