Technical data

1-22
General Information
Model 743 and Model 744 VME Board Computers
HP Parallel The parallel port is compatible with Centronics standards, plus some additional
features found in HP Series 700 workstations. It supports a bi-directional register model
interface. An 8-bit parallel, synchronous interface is used.
A high-density micro D-sub connector is used for the HP Parallel interface. An HP A4300A
adaptor cable is required to convert to standard PC compatible 25-pin female D-sub.
Table 1-17 summarizes the specifications for the HP parallel interface.
PS/2 Ports 1 and 0 There are two PS/2 style serial ports: one PS/2 keyboard port and one
PS/2 mouse port.
RS-232 There are two serial interfaces. The I/O controller ASIC controls port A, and the
VME controller ASIC controls port B. Each supports CTS/RTS hardware handshaking. An
HP A4301A adaptor cable is required to convert it to a standard PC compatible, 9-pin male
D-sub. The maximum baud rate listed in Table 1-18 is the hardware limit. Actual transfer
rates depend upon the operating system and application load.
Table 1-18 summarizes the specifications for RS-232-C.
NOTE: The RS-232 port B is not active until VME Services is up and running.
Battery-Backed Real-Time Clock The battery-backed clock is implemented in the I/O con-
troller ASIC. Once power is applied to the system board, the battery-backed clock time is
read by the operating system only during system initialization. Once the operating system is
booted, real time is kept by using the timer built into the CPU. The battery-backed real-time
clock is updated by the operating system only when the user (“root” or “super-user”) explic-
itly requests it though the date command. The clock has a resolution of 1 second. The accu-
racy of the clock is within ±5 seconds every 24 hours when the operating temperature is from
0 to 55 Deg.C.
Table 1-17 HP Parallel Interface Specifications
Connector type Female 25-pin micro D-sub
Data rate >300 Kilobytes/second with DMA
200 Kilobytes/second sustained
Device limit 1
Type Centronics® and BUSY handshakes
Table 1-18 RS-232-C Interface Specifications
Baud rate 50 to 460.8 Kb/second
Connector type 9-pin female micro D-sub
Controller 16550 UART compatible megacell
Parity Odd, even, none, one, zero
Stop bits 1, 1.5, 2
Type EIA RS-232-C, CCITT V.24/V.28
Word size 5 to 8 bits