Parallel Printer Port Interface - Tandy 1000 SL Technical Reference Manual

Status information reported includes the type and condition of
the ACE'S transfer operations as well as any error conditions
detected during serial data operations. The 8079021 custom IC
includes a programmable Baud Rate Generator that allows operation
from 50 to 9600 Baud. The 8079021 custom IC is supplied with a
clock of 24 MHz from the main Crystal Oscillator. The 8079021 can
be tailored to the user's requirements by being able to remove
start bits, stop bits, and parity bits. It supports
5 , 6 ,
7, or 8
data bit characters with 1, 13, or 2 stop bits. Diagnostic
capabilities provide loopback functions of transmit/receive and
input/output signals.
The 8079021 custom IC serial port is programmed by selecting the
1/0 address 3F8
-
3FE hex and writing data out to the port.
Address Bits AO, Al, and A2 are used to define the modes of
operation by selecting the different registers to be programmed
or read. One interrupt is provided to the system from IRQ4.
Parallel Printer Port Interface
The final
1/0
interface of the Tandy 1000 SL is the Printer
Interface contained in the 8079021 custom IC (U40). This part
supplies all the signals required to interface to a typical
parallel printer. These signals are
8
data out lines, plus
various handshake control signals. Also, the printer interface
generates an interrupt to the CPU if enabled.
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