Martel Electronics 3001 User Manual
Page 51
The Calibrator sends the serial poll status byte (STB) when it responds to a serial poll.
This byte is cleared (set to 0) when the power is turned on. The STB byte structure is
shown in Figure 34. Refer to the *STB? command in section 10 for more information on
reading this register.
7
6
5
4
3
2
1
0
0
RQS
ESB
MAV
EAV
0
0
0
MSS
RQS
Requesting service. The RQS bit is set to 1 whenever bits ESB, MAV, EAV, or ISCB
change from 0 to 1 and are enabled (1) in the SRE. When RQS is 1, the 3001 asserts
the SRQ control line on the IEEE-488 interface. You can do a serial poll to read this
bit to see if the 3001 is the source of an SRQ.
MSS
Master summary status. Set to 1 whenever bits ESB, MAV, EAV, or ISCB are 1 and
enabled (1) in the SRE. This bit can be read using the *STB? Remote command in
place of doing a serial poll.
ESB
Set to 1 when one or more ESR bits are 1.
MAV
Message available. The MAV bit is set to 1 whenever data is available in the 3001's
IEEE-488 interface output buffer.
EAV
Error available. An error has occurred and an error is available to be read from the
error queue by using the FAULT? query.
Figure 34 - Serial Poll Status Byte (STB) and Service Request Enable (SRE) Registers
2) Service Request (SRQ) Line
IEEE-488 Service Request (SRQ) is an IEEE-488.1 bus control line that the 3001
asserts to notify the controller that it requires some type of service. Many instruments
can be on the bus, but they all share a single SRQ line. To determine which
instrument set SRQ, the Controller normally does a serial poll of each instrument. The
calibrator asserts SRQ whenever the RQS bit in its Serial Poll Status Byte is 1. This bit
informs the controller that the 3001 was the source of the SRQ.
The 3001 clears SRQ and RQS whenever the controller/host performs a serial poll,
sends *CLS, or whenever the MSS bit is cleared. The MSS bit is cleared only when
ESB and MAV are 0, or they are disabled by their associated enable bits in the SRE
register being set to 0.
3) Service Request Enable Register (SRE)
The Service Request Enable Register (SRE) enables or masks the bits of the Serial
Poll Status Byte. The SRE is cleared at power up. Refer to Figure 34 for the bit
functions.
4) Programming the STB and SRE
By resetting (to 0) the bits in the SRE, you can mask (disable) associated bits in the
serial poll status byte. Bits set to 1 enable the associated bit in the serial poll status
byte.
5) Event Status Register (ESR)
The Event Status Register is a two-byte register in which the higher eight bits are
always 0, and the lower eight bits represent various conditions of the 3001. The ESR
is cleared (set to 0) when the power is turned on, and every time it is read.
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