CompuPro - Interfacer 4
The Interfacer 4 was fully software
compatibility with the Interfacer 3 as well as the ability to intermix
Interfacer 3 and 4 boards at the same port addresses. Additional features
included 3 fully programmable asynchronous serial channels, 2 of which were
capable of high speed synchronous transmission and one capable of current loop
operation, five RS-232 handshaking lines per channel plus bi-directional
clock drivers on both the synchronous channels, a pin compatible Centronics
parallel interface port with the full complement of handshaking lines, a
universal parallel port with 16 data and 3 handshaking lines, expandability to
32 users with eight boards using only 8 port addresses, a flexible interrupt
structure with full maskability and pending status on both transmit and receive
interrupts, and a conservative design for operation with most CPUs operating to
beyond 10 MHz.
The Interfacer 4 was designed for
efficient operation in interrupt driven/ multi-user microcomputer systems as
well as polled mode single user systems. Eight distinct interrupts are generated
on-board by the three USARTs and two parallel ports, and these are brought out
for jumpering by the user to the eight vectored interrupt lines on the S-100
bus. Since these interrupt lines were open collector, they could be configured
to interrupt on any or all of the vectored interrupt lines. In addition, a
transmit and receive interrupt mask port is provided for inhibiting
unwanted interrupts. The Interfacer 4 provided multi-user operation with a
minimum number of I/O ports by incorporating a user select register to activate
the required I/O channel. This five bit register is used to select a particular
channel, which allows up to 32 users (up to eight boards) on the same 8 port
addresses. When a particular user is selected, the four USART registers
associated with that specific serial channel or the parallel registers are made
available for examination and alteration by the host processor or other
temporary bus master. In addition, whenever a particular channel is selected,
the interrupt registers on that particular board as well as the registers on
another board in the same group of eight users are available for
examination and alteration. This was a very cleaver idea used on later
S-100 boards and got around the dwindling I/O space becoming available on the
bus. The board utilized INS 2651 UARTS.
The manual for this excellent board can
be found here.
This page was last modified
on
01/08/2011