11A34: Difference between revisions

The M377's - input is connected to the [[ACVS]] (Analog Control Voltage System) output.

The (differential) display outputs of the four amplifiers are hard-wired in parallel and drive the mainframe’s  

50 Ω per side input impedance.  The same is true of the trigger outputs of the four amplifiers.

The version of the M377 used in the 11A34 has a 200 Ω output impedance per side so that four of them in parallel  

create a source impedance of 50 Ω.

Each M377 amplifier's nominal common-mode output voltage is zero whether enabled or not. When not enabled, each M377

differential output is exactly zero by design. This fact is used during calibration by the plugin’s firmware to  

determine the mainframe’s imbalance and compensate for it during normal operation.

Each of the four channels has its own AUX output on dedicated pins of the plug-in interface connector:

ROM size.  [[Doug Haines]] found an alternate supplier of 8051-compatible chips (OKI Semiconductor)

that offered a 16Kbyte on-chip ROM, and that's what the plug-ins wound up with. The finished code size wound up at about 14 KB.

The 11A34 also contains a Dallas Semiconductor DS1220Y NVRAM storing last settings, calibration constants, and instrument serial number.   

The DS1220Y contains a battery with a typical life time of 20-30 years.   

There are also two [[ACVS]] (Analog Control Voltage System) sample and hold modules on two daughter boards that generate the analog voltages needed for gain and offset, including error correction  

under microcontroller firmware control.   

The microcontroller also provides the digital signals sent to the M377 amplifier, setting one of its six fixed gains, one of its three bandwidths, turning on or off its selected output, and each output's + up or invert state.