Specifications

System Registers 7-83
GBUS$SERNUM
Table 7-39 GBUS$SERNUM Register Bit Definitions
A
ddress
A
ccess
FF C700 0000
R/W
The GBUS$SERNUM register is used to read and write an SROM
on the clock module where the system serial number is stored. All
reads and writes to this register are done by software.
43 0765 12
BXB-0728-93
SROM_CLK
RCV_DATA
XMT_DATA
STP
PIUA
PIUB
EXPSEL
Name Bit(s) Type Function
STP
PIUA
PIUB
<7>
<6>
<5>
R/W, 0
R, 0
R, 0
Self-Test Passed. Drives large green STP LED on
the CPU module.
PIUA Status. Depending on the system configura-
tion, this bit indicates that the peripheral unit
marked as A has power status OK, or that AC is
failing. Writing one to this bit enables power-fail
interrupts to the DECchip 21164 based on a change
of state of <PIUA>. Note that a read of the bit
yields the PIU status, not the interrupt enable
state. Writing zero to this bit turns off power-fail
interrupts to the DECchip 21164.
PIUB Status. Depending on the system configura-
tion, this bit indicates that the peripheral unit
marked as B has power status OK, or the battery
charge is low, or one of the regulators has a prob-
lem.