HP 8112A, Operating, Programming And Servicing Manual

Page: 83 / 406

Hardware Settling Time
Error, Fault and
Status Reporting
HP-18 Status Byte
The timings given are worst case. When parameter settings
are combined into one programming message, the combined
implementation time can be up to
40%
more efficient.
The Buffer Not Empty flag in the HP 81 12A status byte is set during
this time. The system controller can therefore monitor this flag to
detect when a programming message has been implemented. Refer to
"Error, Fault and Status Reporting" .
The hardware requires time to settle after a change. This sometimes
takes longer than the time taken to interpret and execute the
message, typically < 5 ms.
The HP 81 12A is provided with the capabilities of requesting service
from the controller (the computer) whenever the instrument detects
an error.
To be able to determine if an error was caused, Status Reporting
Structures are required. For this purpose the instrument contains the
Status Byte register:
The Status Byte Register (STB) is composed of seven single-bit
"summary-messages" . Each of the bits
0
thru 5 summarizes a specific
type of error. For example, bit
0
represents all types of Limit errors.
(See the operating manual of the HP 81 12A) Bit
6
of the STB is the
Request Service (RQS) Bit and is set whenever a service request is
caused. Bit
7
indicates whether the Buffer is empty or not.
After a Serial Poll (SPOLL) the complete Status Byte is cleared.
The Status Byte is updated after every command received by the HP
81 12A.
The HP 81 12A status byte can be read using a serial poll.
A = SPOLL (712)
PRINT 118 1 12A Status Byte= 11 ; A
Read instrument status byte
into variable A
The meaning of each bit in the status byte is given below. In all
cases, the bit is set to 1 to indicate that the condition described is
true.
Programming 6-13