Usb Operation; Introduction; General Features; Terminator, Status Byte, And Overload Byte - Ametek 7124 Instruction Manual

6.4 USB Operation

6.4.01 Introduction

6.4.02 General Features

6.4.03 Terminator, Status Byte, and Overload Byte

terminal, or a simple computer-based terminal emulator, to the RS232 port. Where
the prompt is not required it can be suppressed by setting the noprompt bit, bit 4 in
the RS232 parameter byte. The default (power-up) state of this bit is zero.
Because of the limited number of bits in the status byte, it can indicate that an
overload exists but cannot give more detail. An auxiliary byte, the overload byte
returned by the N command, gives details of the location of the overload.
A summary of the bit assignments in the status byte and the overload byte is given in
table 6-1 below.
Bit Status Byte
bit 0 command complete
bit 1 invalid command
bit 2 command parameter error
bit 3 reference unlock
bit 4 output overload
bit 5 new ADC values available
after trigger
bit 6 input overload
bit 7 data available
Table 6-1, Status and Overload Byte Bit Definitions
The USB interface in the instrument supports operation at both Full and High Speed
settings. It provides two bulk data transfer endpoints, with endpoint 1 being used to
send commands to the instrument, and endpoint 2 being used to receive responses
from it.
Operation of the instrument via the USB is made a great deal simpler if the user
installs the relevant SIGNAL RECOVERY USB driver software. Two versions of
driver are available; the first, a bulk USB driver SRUSBXP.SYS is compatible with
several software packages supplied by SIGNAL RECOVERY, while the second,
based on National Instrument's VISA software, allows operation both from
SIGNAL RECOVERY software and a free LabVIEW driver. The only disadvantage
of using the VISA software driver is the need to download and install the complete
VISA environment in order to use the driver.
Readers should refer to the document "USB Drivers for the Model 7124 and 7270
Lock-in Amplifiers", available from the www.signalrecovery.com website, for
further information about installing these drivers.
Unlike the RS232 interface, there is no difficulty ensuring that the correct cable type
is used for USB operation. All that is required is a standard USB-A to USB-B cable,
which if the driver is correctly installed on the computer will then allow operation
without further adjustment.
Commands sent to the instrument over the USB interface should be terminated with
a null character (ASCII 0).
Chapter 6, COMPUTER OPERATION
Overload Byte
X(1) output overload
Y(1) output overload
X(2) output overload
Y(2) output overload
CH1 output overload
CH2 output overload
CH3 output overload
CH4 output overload
6-5