Introduction
2 – Overview
VL-486-4 Reference Manual
O
N
-B
OARD
M
EMORY
RAM
Two 42-pin
SOJ JEDEC
compatible sockets accept up to two 1M x 16 dynamic
RAM
chips
to provide a total of 2M or 4M of 16-bit system memory. The use of 1M x 18
RAM
chips will
provide parity error detection if desired.
ROM
Two 32-pin
PLCC JEDEC
compatible sockets accept one or two high density memory
components including 128K x 8, 256K x 8, and 512K x 8
EPROM
s and Flash
EPROM
s. You can
start out with one device, and add a second one when your storage requirements grow. A Flash
File System is available to make the Flash device(s) appear as a bootable disk drive.
H
ARD
D
ISK AND
F
LOPPY
D
ISK
I
NTERFACE
The VL-486-4 does not have hard disk or floppy disk interfaces. A Flash File System is included
which allows the CPU to boot from Drive A. Software is pre-installed on the FFS to network the
CPU with a desktop IBM PC using RS-232.
D
IGITAL
I/O (O
PTO
22) I
NTERFACE
A 34-pin Opto 22 compatible interface is included on the VL-486-4 card for connection to
industry standard Opto 22 I/O racks. The interface can also be used for general TTL interfacing.
A rack power output provides up to 1A at +5V (typical). The power supply line is protected by a
self resetting circuit breaker.
COM P
ORTS
The two on-board COM ports are hardware and software compatible with the PC/AT
architecture. Baud rates are programmable from 50 baud to 115K baud. COM1 is a standard RS-
232 interface, COM2 can be jumpered for RS-232, RS-422, or RS-485 operation.
P
ARALLEL
P
ORT
The bi-directional parallel port can be used as a standard PS2 compatible LPT port or as 17
general purpose TTL I/O signals. Each output line has a 24 ma current sink rating. Eight of the
signals are programmable as a group for input or output, three are dedicated output, and five are
dedicated inputs. A strobe signal, which produces a 50
µ
s pulse under program control, is also
available as an output.
C
OUNTERS
/T
IMERS
The VL-486-4 card includes three 8254 type 16-bit counter/timers. One channel provides timing
for dynamic
RAM
refresh, one channel generates an 18.2 ms DOS interrupt, and another channel
is used to drive the speaker. All channels are available for general purpose timing and periodic
interrupt sources if they are not being used by an operating system.
Also included are three 16-bit counter/timers embedded within the Zilog 8536 Digital I/O chip.
Four control signals for each of these counter/timers are available on an external connector.