MODEM CONTROLLER II.

T.O. 31S5-4-305-l

TM 11-5805-663-14-13

NAVELEX 0967-464-0010

5-99. MODEM CONTROLLER 2 (ACOC

Group only). The Modem Controller 2 func-

ed to generate or pre-

tion receives S-bit bytes of data from the

ting a level 2 interrupt--

INFIBUS and converts these bytes to serial

words that are routed to the VF Comm Link 2

function. It also receives serial words

from the VF Comm Link 2 function and con-

verts these words to 8-bit bytes of data that

are placed on the INFIBUS. Modem Control-

ler 2 is a slave that generates a level 2

interrupt and is assigned address F94X 16.

{reads status register)

There are three registers located in Modem

a data transfer is to

en The RO TTY function

Controller 2; the data register, control reg-

ister, and status register. Each register is

notifies the Printer Controller that data is

assigned a separate address which allows

a programmed data trans-

the stored software program to write into or

bit is set in the status

read from each register as determined by the

en the CPU detects the PDT

level of RITE-N. The data register is assigned

status bit, the CPU jumps to a subroutine

address F948 16. The control register address

a write or read

determines wh

Whi

is F946 16, and the status register is F940 16.

e d . If a write

ion IS to be pe

ope

operation is to be performed by the CPU,

5-100. If the stored software program is to

the CPU places the data register address

clear Modem Controller 2, F940 16 is plated

on the INFIBUS address lines, places the

on the INFIBUS address lines, ABOO-N

data on the INFIBUS data lines, and gener-

through AB15-N, no data is placed on the

ates RITE-N. The data is loaded into the

INFIBUS data lines, DBOO-N through DB15-N,

Printer Controller which then generates

and a write operation (RITE-N low) is per-

DONE-N to free the INFIBUS. The Printer

Controller now converts the parallel input

formed. This write operation to the status

data from the INFIBUS to serial data that IS

Controller 2 then generates DONE-N which

clocked to the RO TTY function. If a read

frees the INFIBUS.

o p e r a t i o n i s t o b e p e r f o r m e d , the CPU

places only the data register address on the

5 - 1 0 1 . The stored software program can

INFIBUS address lines and the serial data

also read from or write into the control reg-

from the RO TTY function which has been

ister, as determined by the level of RITE-N,

converted to an 8-bit parallel byte is

by placing the control register address on

strobed to the INFIBUS data lines. The

the INFIBUS address lines. After the control

Printer Controller then generates DONE-N

to free the INFIBUS.

Controller 2 operates DONE-N which frees

If the level 2 interrupt is enabled by

5-97.

the INFIBUS.

the control word in the control register,

whenever the PDT status bit is set, a level

5 - 1 0 2 . Under control of the CPU, Modem

2 interrupt is generated, as explained pre-

The CPU then addresses the data

Controller 2 is enabled to generate or pre-

VlOUSly.

vented from generating a level 2 interrupt

whenever data is to be transferred by

ation in the same manner as when the level

Modem Controller 2. The control word that

2 Interrupt w a s d i s a b l e d .

has been loaded into the control register

5-98.

T h e baud rate of the Printer Controller

enables or disables Modern Controller 2

INFIBUS access circuits which generate the

is controlled by a signal from the RO TTY

function which is derived from the line fre-

level 2 interrupt. If the level 2 interrupt is

disabled by the control word, the CPU reg-

q u e n c y . Therefore, if the line frequency

ularly checks status (reads status register)

varies which in turn varies the speed of the

RO TTY motor, the baud rate varies propor-

to determine whether a data transfer is to

be performed. When the VF Comm Link 2

tionately.

5-15