I/O Section; Serial Ports Generally - Vector ZCB User Manual

Vector ZCB Single Board Canputer
dynamic memories, such as Vector Graphic's
64K
meJTK)ry board. Simplicity of
design has been stressed to enhance reliability of operation by the use of
MSI and ISI integrated circuits.
1.4 PID1/RAM section
The PROM/RAM section features lK of on-board RAM memory (using 2114's)
and up to 12K of PRCM, RCM or EPRa1. Note: For the purposes of discussion
in this manual, the terms PROM, EPRCM and Ra1 may be used interchangably.
Their technical distinction makes no difference in how they are used in the
ZCB. The PROM may be implemented using either 2708's, 2716's or 2732's.
This allows the user maximum flexibility with regard to choice of operating
systems, languages, etc. Several jumper options such as jump on
power-on/reset are available. Advanced address decoding logic permits a
wide range of addressing options.
1.5 I/O section
The I/O section of the ZCB single board computer offers three 8-bit
parallel ports or ports programmable as input or output and one RS-232C
level serial port for interfacing with multiple perpheral devices such as
printers, modems and terminals.
The CPU sends data to the serial and parallel ports via I/O addresses.
The I/O addresses used by the board can be changed as a group. The board
uses eight I/O addresses from
DOH
to FFH. You specify the value of the
addresses by jumper(s), as listed in Section 2.4.1. Thus, the entire range
of 256 possible port addresses may
be
accessed with the advanced decoding
logic built into the Vector Graphic ZCB.
The ZCB Board does not
cane
with any software for specific applications,
though Vector Graphic supplies certain items of software that make use of
its features. The Vector Graphic Extended Systems Monitor 4.0 will work with
the board as it corres fran the factory without any modification.
1.5.1 serial ports generally
Discuss ion of the serial port centers around the industry standard 8251
USARr (Universal Synchronous/Asynchronous ReceiverjTransmitter) chip. Much
of the flexibility of the ZCB board derives fram the flexibility of this
chip and its parallel counterpart, the 8255, both of which can be modified
via software. You, through software, can control the rate of serial
transmission, and the format of the transmitted data. Data is transmitted
as ASCII code having between 5 and 8 bits per character, with an optional
added-on parity bit (choice of even or odd), and with one start bit and a
choice of one, one and a half, or two stop bits per
c~aracter.
Further,
using the 8251, the board can handle either asynchronous or synchronous
communication. Baud rates, format, handshaking, and whether ccmnunication
is asynchronous or synchronous, is specified through software and, in some
cases, hardware modifications.
1-2
Rev. l-B 6/11/80