Z80185 Datasheet, PDF (25/95 Pages) Zilog, Inc. – SMART PERIPHERAL CONTROLLERS

Zilog
PRELIMINARY
Z80185/Z80195
SMART PERIPHERAL CONTROLLES
PIN DESCRIPTIONS (Continued)
EMSCC Signals
/RTS. Request to Send (output, active Low). When the
Request to Send (RTS) bit in Write Register 5 is set, the
/RTS signal goes Low. When the RTS bit is reset in the
Asynchronous mode and auto enables is on, the signal
goes High after the transmitter is empty. In Synchronous
mode, or in Asynchronous mode with auto enables off, the
/RTS pin strictly follows the state of the RTS bit. Thus the pin
can be used as a general-purpose output. In a special
“AppleTalk” mode on the Z80185, the pin is under hard-
ware control.
/DTR. Data Terminal Ready (outputs, active Low). The
“/DTR//REQ” functionality found in other SCC family mem-
bers has been reconfigured internal to the EMSCC
megacell. The /DTR output is routed to this pin, while the
/REQ signal is routed to the DMA request multiplexing
logic as described in a later section on the EMSCC. This
pin follows the state of the DTR bit in WR5 of the EMSCC.
Note: The /W/REQ pin present on other SCC family mem-
bers has its two possible functions reconfigured internal to
the EMSCC, and both functions are handled internally to
the Z80185. The Wait output of the EMSCC drives the
/WAIT signal in a wire-ORed fashion with other internal and
external peripherals. The /REQ component is routed to the
DMA request multiplexing logic as described in a later
section on the EMSCC.
Z80185 Parallel Ports
PIA16-14. Port 1, Bits 6-4 or CTC ZC/TO2-0 (input/output).
These lines can be configured as inputs or outputs, or as
the “zero count/timeout” outputs of three of the four CTC
channels, on a bit-by-bit basis.
PIA13-10. Port 1, Bits 3-0 or CTC CLK/TRG3-0 (input/
output). These lines can be configured as inputs or out-
puts, or as the “clock/trigger” inputs of the four CTC
channels, on a bit-by-bit basis.
PIA27-20. Port 2, Data, or Bidirectional (input/output).
These lines can be configured as inputs or outputs on a bit-
by-bit basis when not used for Bidirectional Centronics
operation. However, when used for Bidirectional Centronics
operation, software and hardware controls the direction of
all eight as a unit.
Bidirectional Centronics Pins
nStrobe, nAutoFd, nSelectIn, nInit (input/outputs). These
are inputs when using P27-20 for the Peripheral side of a
Centronics controller, or outputs when using P27-20 for the
Host side of such an interface. In certain P1284 modes,
these pins assume other names as described in the
section on the Centronics P1284 controller. When not
using P27-20 for a Centronics controller, these pins can be
used as general-purpose inputs or outputs.
Busy, nAck, PError, nFault, Select (input/outputs). These
are outputs when using P27-20 for the Peripheral side of a
Centronics P1284 controller, or inputs when using P27-20
for the Host side of such an interface. In certain P1284
modes, these pins have other names as described in the
section on the Centronics P1284 controller. When not
using P27-20 for a Centronics P1284 controller, these pins
can be used as general-purpose outputs or inputs. These
pins always function in the opposite direction of the pre-
ceding group.
DS971850301
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