Control Register - HP E1399A User Manual

Control Register

Chapter 2
The Control Register is an 8-bit register which causes specific actions to be
executed by the breadboard module when written to from the backplane
data bus. The primary component of the Control Register is U13, as shown
in Figure 2-10. Table 2-9 shows the part number for U13.
Table 2- 8. Control Register Bit Definitions
Data Bit(s)
CR0
CR1
CR2-CR7
Table 2-9. Control Register Parts
Reference HP Part Number
Designator
U13 1820-4086
Figure 2-10. Control Register
Table 2-8 shows the Control Register bit definitions. The Control Register
is selected for writing to by the BASE+4 enable line (see Table 2-2).
BASE+4 going low at the input of U21C, combined with a negative pulse
(for one clock cycle of SYSCLK) from the LATCH* output of U6 (also
applied to U21C), provides a positive-going edge clocking pulse
(CONTROL) to U13. This pulse clocks whatever is present on DB0-DB7
through U15 to the Control Register access points (CR0-CR7).
Definitions
CRESET (software reset)
SYSFAIL INHIBIT
Device Dependent (User assignable)
Description
IC, 74H( T~73 Octal D-Type Flip Flop
Configuring the HP E1399A 29