HP 743 Series Technical Reference Manual For Oems page 31

General Information
Model 743 and Model 744 VME Board Computers
HP Parallel
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.
Table 1-17 HP Parallel Interface Specifications
Connector type
Data rate
Device limit
Type
PS/2 Ports 1 and 0
PS/2 mouse port.
RS-232
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.
Table 1-18 RS-232-C Interface Specifications
Baud rate
Connector type
Controller
Parity
Stop bits
Type
Word size
Battery-Backed Real-Time Clock
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.
1-22
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The parallel port is compatible with Centronics standards, plus some additional
Female 25-pin micro D-sub
>300 Kilobytes/second with DMA
200 Kilobytes/second sustained
1
Centronics® and BUSY handshakes
There are two PS/2 style serial ports: one PS/2 keyboard port and one
There are two serial interfaces. The I/O controller ASIC controls port A, and the
50 to 460.8 Kb/second
9-pin female micro D-sub
16550 UART compatible megacell
Odd, even, none, one, zero
1, 1.5, 2
EIA RS-232-C, CCITT V.24/V.28
5 to 8 bits
The battery-backed clock is implemented in the I/O con-