Z80 Datasheet, PDF (323/330 Pages) Zilog, Inc. – Z80 CPU PERIPHERALS

Z80 CPU Peripherals
User Manual
303
The Z80 DMA controller circuit is used with Z80 SIO/2 to transmit the
reformatted data at high speed with the required protocol. The high-speed
modem provides the transmit clock for this channel. The Z80 CTC counter-
timer circuit supplies the transmit and receive clocks for the low-speed
lines and is also used as a time-out counter for various functions.
Z80 SIO/1 controls local or remote terminals. A single intelligent terminal
is placed within the dashed lines. The terminal employs a Z80 SIO to
communicate to the data concentrator on one channel while providing the
interface to a line printer over its second channel. The intelligent terminal
could be designed to operate interactively with the operator.
Depending on the software and hardware capabilities built into this system,
the data concentrator can employ store-and-forward or hold-and-forward
methods for regulating information traffic between slow terminals and the
high-speed remote processor. If the high-speed channel is provided with a
dial-out option, the channel can be connected to a number of remote
processors over a switched line.
UM008101-0601
Serial Input/Output