user manual

B
B-1
BSerial Interconnections
Introduction
As described in previous chapters of this manual, the MVME2603/2604
serial communications interface has four ports. Two of them are combined
synchronous/asynchronous ports; the other two are asynchronous only.
Both synchronous and asynchronous ports supply an EIA-232-D
DCE/DTE interface via P2 and the MVME712M transition module.
Asynchronous Serial Ports
The MVME2603/2604 uses a PC87308 ISASIO chip from National
Semiconductor to implement the two asynchronous serial ports (in
addition to the disk drive controller, parallel I/O, and keyboard/mouse
interface).
The asynchronous ports provided by the ISASIO device are routed through
P2 and the associated transition module. The TTL-level signals from the
ISASIO chip are buffered through TTL drivers and series resistors, then
routed through EIA-232-D drivers and receivers to complete the
asynchronous serial interface enroute to the MVME712M transition
module.
The MVME2603/2604 hardware supports asynchronous serial baud rates
of 110B/s to 38.4KB/s. For detailed programming information, refer to the
PCI and ISA bus discussions in the MVME2600 Series Single Board
Computer Programmer’s Reference Guide, listed in Appendix D, Related
Documentation, and to the vendor documentation for the ISASIO device.
Synchronous Serial Ports
The MVME2603/2604 uses a Zilog Z85230 ESCC (Enhanced Serial
Communications Controller) with a 10 MHz clock to implement the two
synchronous/asynchronous serial communications ports, which are routed
through P2 to the transition module. The Z85230 handles both