BUS CONTROLLER-CONT. - TM-11-5805-663-14-130057

T.O. 31S5-4-308-1

TM 11-5805-663-14-13

NAVELEX 0967-464-0010

Controller generates SACK-N which will

request line is activated by the CPU and

abort the selection cycle. The function

detected by the Bus Controller.

requesting the INFIBUS access must then

reinitiate the request.

5 - 3 2 . The precedence pulse, PCDA/B-P is

chained through all functions of the Pro-

5-34. After the selected master generates

cessor and determines which function (when

SACK-N, SRLD-N is removed. The Bus Con-

more than ore function is requesting the

troller senses SACK-N and the removal of

INFIBUS on the same priority level) will gain

SRLD-N and then removes SELD-N. The

INFIBUS access first. The precedence pulse

selected master monitors STRB-N and when

is referred to as PCDB-P when generated by

STRB-N is removed, the address, control,

or exiting from a function and PCDA-P when

and data (if a write operation) is placed on

entering a function. Assume that two func-

the INFIBUS. The selected master places

tions, the Parallel I/O and TTY Controller,

the address on the INFIBUS address lines,

are requesting INFIBUS access. SRL1-N is

AB00-N through AB15-N (waveform E, figure

generated by both functions and is detected

3 ) . If the master is to write data into the

by the Bus Controller. The Bus Controller

function being slaved (addressed), it gen-

generates the select line, SEL1-N, and

erates RITE-N (waveform F, figure 3). If it

PCDB-P. PCDA-P is coupled through and

is to read data from the function being slaved,

delayed by the CPU and Autoload functions

it holds the RITE-N line high. If the data

and trapped by the Parallel I/O. Trapping

being transferred is a 16-bit word, the

the precedence pulse enables the Parallel

master holds BYTE-N high and data lines,

I/O to gain INFIBUS access first. When the

DB00-N through DB15-N (waveform G, fig-

Parallel I/O completes its transfer, the Bus

ure 3), are used. If the transfer is to be an

Controller generates PCDB-P again (SRL1 -N

8-bit byte, the master generates BYTE-N

still being generated by TTY Controller)

and only 8 data lines, DB00-N through

which is trapped by the TTY Controller.

DB07-N, are used. The selected master

The precedence pulse serves to grant

now generates STRB-N which allows the

INFIBUS access to the function nearest the

requested data transfer to occur (service

Bus Controller first when two or more func-

cycle) and removes SACK-N which allows

tions are requesting INFIBUS access on the

the Bus Controller to select the next master

same priority level.

if it is requesting INFIBTUS access.

5 - 3 3 . When one or more masters are re-

5 - 3 5 . If a second master is requesting

questing a DDT, the master or masters

INFIBUS access, the Bus Controller selects

generate SRLD-N (waveform A, figure 3).

this function in the same manner it selected

The Bus Controller senses SRLD-N and

the first master. While the second master

selects SRLD-N over other requests. The

function is being selected, the slave (ad-

Bus Controller then generates the select

dressed) function of the first master func-

signal, SELD-N (waveform B, figure 3),

tion recognizes its address on the INFIBUS

and the precedence pulse, PCDA-P (wave-

and the data is written into or the data

form C, figure 3). SRLD-N is received by

(waveform I, figure 3) is read out of the

all of the masters requesting INFIBUS access

s l a v e . When the data transfer is complete,

but PCDA-P reaches the master nearest the

the slave generates DONE-N (waveform J,

Bus Controller first. This master prevents

figure 3) which causes the first master to

the precedence pulse from being coupled to

remove the address, control, and data (if a

the other masters. The master requesting

write operation) from the INFIBUS. Receiving

the INFIBUS access now generates SACK-N

DONE-N also causes the master to remove

(waveform D, figure 3) which notifies the

STRB-N from the INFIBUS. The second se-

BUS Controller of a successful selection and

lected master function senses the removal

prevents other functions from requesting

INFIBUS access during the time it is glen--

of STRB-N and places address, control and

era ted. If SACK-N is not sensed by the Bus

data (if a write operation) signals on the

INFIBUS and a data transfer occurs as ex-

Controller within 2 microseconds after

plained for the first master. Upon comple-

SELD-N and PCDA-P are generated, the Bus

5-5