HP 3457A Service Manual page 185

information from data bus "A", lines DO through D7.
8-45. Writing information to RAM U506.
To store information in RAM U506, the microprocessor:
© Sets the read/write (k/W) output (U5O1, pin 32) low.
8-46. Writing to the unprotected section of RAM U511.
© Sets address lines Al4 high and A15 low to enable decoder U513.
8-47. Writing to the protected section of RAM U511.
The "Write to CAL-RAM"
sequence begins with a CAL command, either from the interface bus or
from the front panel.
The microprocessor is reset prior to each calibration routine to insure that valid
measurements are obtained.
HP 3457A Multimeter
8-20