BVME4000/6000
6
Copyright
1993,1995,1998,2001 BVM Ltd.
3.5 Serial
Communications
Two serial communications interfaces are provided from a Z85230 SCC device. The Z85230 provides
both synchronous (SDLC/HDLC) and asynchronous protocols. Asynchronous baud rates of up to
115.2Kbit/s (using the on-board crystal) are supported. Field changeable buffer modules allow RS232,
RS422 or RS485 electrical interfaces to be selected for either (or both) channels. The two serial
interfaces are available on the front panel, or via the rear P2 connector. The synchronous clock
signals are also available via the P2 connector.
3.6 Parallel
Port
An 8-bit, bi-directional I/O port with interrupt driven handshake is provided allowing direct connection to
Centronics devices. This is implemented in a 68230 which includes a further 24-bit timer with interrupt
capability. This device also provides part of the board control functions, and is used to control the
software watchdog function. The parallel port is connected to a dedicated connector near the front
panel, or via the P2 connector.
3.7 SCSI
Interface
A SCSI interface is provided built around the NCR53C710. This provides asynchronous transfers of up
to 5Mbytes per second. The 32-bit DMA driven interface allows direct access to the entire memory
map of the BVME4000/6000. The burst mode interface stacks up 16 bytes at a time and transfers
them as a line transfer at up to 4/2/2/2 access speeds at 25MHz bus clock. At 5Mbyte/s this gives a
400nS burst every 3.2
µ
S or 12.5% bus bandwidth requirement. The 53C710 is an intelligent processor
in its own right, running SCSI SCRIPTS software. This enables very high level commands to be issued
to the SCSI interface further minimising processor overhead. The SCSI interface is connected to a
dedicated 50-way connector and is also available via the P2 connector.
3.8 Ethernet
Interface
An Ethernet Interface is provided built around the Intel 82596CA. This provides a 32-bit DMA driven
interface to both Ethernet (via the AUI interface on the P2 connector) and either Cheapernet (via a
front panel BNC) or optionally 10BaseT (via a front panel RJ45). The 32-bit DMA driven interface
allows direct access to the entire memory map of the BVME4000/6000 allowing full packet
management by the 82596CA. Each 32-bit transfer requires 320nS maximum (including arbitration) to
execute the cycle. A transfer will occur no more frequently than every 4
µ
S (4 bytes at 1Mbyte per
second). Thus worst case bus bandwidth requirement is 8% at 25MHz bus clock.
3.9 IP
I/O
Two standard IP compatible sites are provided. The IP interface complies fully with the IP
specification. The two sites may be used individually for single IP's which are accessed as 16-bit wide,
or as a pair for double IP's, which are accessed as 32-bit wide. IP
operation is supported at 8MHz,
32MHz, and CPU synchronous speeds. The IP DMA function is not supported by these two sites, but
may be supported on an IP daughter board (see below). The IP ID and I/O spaces are 256bytes each,
and the memory spaces are 8Mbytes. IP vectored interrupts are fully supported and the interrupt levels
may be individually programmed.
An IP expansion bus connector is provided to allow additional IP's to be supported. A further 4 IP's
may be added on a daughter board connected to this expansion interface. Two 'virtual IP' sites are
also available for controlling the daughter board IP interface. The daughter board may include a local
DMA controller and RAM which is accessed through one of the 'virtual IP' sites, thus supporting the IP
DMA function.
