Specifications

7-84 System Registers

Table 7-39 GBUS$SERNUM Register Bit Definitions (Continued)

Name Bit(s) Type Function

EXPSEL

XMT_DATA

RCV_DATA

SROM_CLK

<4:3>

<2>

<1>

<0>

R/W, 0

W, 1

R, 1

W, 1

Expander Select. Selects which cabinet the

power supply UART lines are logically connected to

and, therefore, which set of three 48V power sup-

plies are connected to the PS lines. May be used by

console when TLDIAG<FRIGN> is set for commu-

nication between the CPUs.

Transmit Data. This bit must be set to receive

data from RCV_DATA.

Receive Data.

Serial ROM Clock.

EXPSEL Selection

PS lines talk to the main CPU

cabinet.

PS lines talk to the right ex-

pander cabinet.

PS lines talk to the left ex-

pander cabinet.

PS transmit line is looped back

to PS receive line.