EXFO T100S-HP Series, Руководство по программированию, Страница: 9 / 40

Remotely Controlling the T100S-HP
T100S-HP Programming Guide 9
1.2.1 Checking System Status with the Status Byte
Definition of the
Status Byte The status byte is an 8-bit value that reflects the status of the T100S-HP
.
It contains a
number of binary indicators, which can be used by the computer for optimal
synchronization with the T100S-HP product. They indicate to the computer the nature of
the current operations as well as the errors encountered.
The only way to read the status byte is to perform an operation called serial polling.
If a condition is in effect, the corresponding binary indicator takes a bit-value of
1
otherwise, the default bit-value is
0
.
Bit Position Indicator Meaning
#7 (MSB) (Bit not used) Bit 7 is not used.
#6 SRQ
(Service ReQuest) This line is part of the definition of the IEEE-488.1
standard. It can be triggered by any device on the
bus. It alerts the central controller that a particular
device requests to perform a specific operation.
When the controller detects that the SRQ line is
active, it can probe all of the devices present on the
bus to determine which device has initiated the
service request and for what reason. This operation
by which the controller reads the status byte of each
device is called "serial polling". The controller then
monitors the bit-value of each indicator within the
status byte.
The IEEE-488.1 standard specifies that when a
device sends a service request, bit-value #6 is set to
1
. The other bits of the status byte can reflect the
state of different logical indicators of the system.
• Set to
1
if a service request has been sent by
the product.
• Set to
0
cleared when the bus controller reads
the status register.
#5 ESB Reserved for future use.
#4 MAV
(Message AVailable) • Set to
1
if a message is placed in the output
buffer. This bit remains set to "1" for as long as
the output buffer is not polled.
• You can to clear the buffers so that any
message is flushed (see section
IEEE Standard
Functions, p. 18 , function
Clear
)
#3 LIM
(Current LIMitation) • Set to
1
if the T100S-HP has reached its current
limit while in APC mode. The bit is only lifted
once the current limit is reached. When sending
a Power or Current command, this bit is usually
set a short delay after the OPC bit is set back to
1
. This is because the laser actively and
continuously monitor its current and as it
evolves, the limit can be reached. This can
happen after the "Power" or "Current" command
is considered "completed".
• Set to
0
in all other cases.