SERIAL I/O CONTROL GROUP ASYNCHRONOUS DATA TRANSFER CONTROL CIRCUIT

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

TM 11-5805-663-14-13

NAVELEX 0967-464-0010

circuit controls the transferring of data to

G5 and RLOP-P enables G10. TRAC-N,

or from the external device. Control words

RLPR-N and BARL-N are routed to the data

from the control register circuit enable the

multiplexers U56, U58, U67, and U68.

asynchronous data transfer control circuit

5 - 4 9 7 . The asynchronous data transfer

to perform write or read operations. In a

control circuit generates RCBC-N and

write operation, the asynchronous data

TRST-N. RCBC-N clears the data shift

transfer control circuit controls the con-

version of parallel data in the data selector/

asynchronous data transfer control circuit

control circuit to serial data for transmis-

then generates TRSE-P and TRSA-N. TRSE-P

sion to the external device. In a read opera-

enables G6 and TRSA-N enables the data

tion, the asynchronous data transfer con-

shift register to shift to the left.

trol circuit controls the conversion of

serial data from an external device to

5 - 4 9 8 . Serial data from the external de-

parallel data to be stored in the data

vice is routed to flip-flop FF4, either

selector/control circuit.

directly or via inverter I2. When the start

bit of the word from the external device is

5 - 5 0 3 . Detail Analysis (see figure 70).

received, FF4 is cleared which disables

When the master reset pulse is generated

G5 and activates G10. G5 presents a high

on the INFIBUS or when the status register

to the SDLS input of data shift register U77

is written, the control register circuit

and G10 causes a 0 to be coupled back to

generates RNIN-N and TNOT-N. RNIN-N

the external device.

resets flip-flops FFl, FF2, FF4, FF5, and

activates gate G13 which resets flip-flop

5 - 4 9 9 . The data shift register U77 is

FF3. TNOT-N presets flip-flop FF6 and

clocked which causes it to shift to the

resets flip-flops FF7 and FF8. The 1 out-

left as explained during a write operation

and the serial data is loaded into it. When

put of FF6 enables gate G8.

the start bit is in the DOOS-P position

5 - 5 0 4 . With a write operation control

(high), the set input of FF3 is enabled.

word stored in the control register circuit,

FF3 is set, as explained previously, which

generates DSTS-P and the stop bit of the

RNIN-N, TOTR-N and TOTS-P are gener-

ated. RNIN-N holds FFl through FF5 reset.

word received causes FF4 to be set which

generates RDST-P and RDTR-N. DSTS-P,

TOTR-N activates gate G4 which enables

RDST-P, and RDTR-N are routed to the

the binary counter U42 to be triggered by

asynchronous data transfer circuit which

CLCK-P from the clock generator circuit

removes TRSE-P and TRSA-N.

and TOTS-P enables gate G14. With TNOT-N

high, the preset input of FF6 and reset

5-500. When the Serial I/O is addressed

inputs of FF7 and FF8 are disabled.

to read out data stored in the data shift

5-505. When the external device is ready

causes MPXA-P and MPXB-P to go low and

to accept data, the control register circuit

generates BDIN-P. This causes the data

generates TOAK-P which activates G8. G8

multiplexers U56, U58, U67 and U78 to

generates BTRQ-N to the data selector/

couple 1CO and 2CO inputs, DOOS-P

control circuit and to the INFIBUS access

through D07S-P, and the 1Y and 2Y outputs,

circuit which generates an interrupt request.

DDOO-N through DD07-N. BDIN-P strobes

data bus driver/receivers which couples

5 - 5 0 6 . The binary counter U42 is a divide

DDOO-N through DDO7-N to the INFIBUS as

by 16 counter which counts every high-to-

DBOO-N through DB07-N, respectively.

low transition of CLCK-P from the clock

generator circuit. It provides a 4-bit

5-501.

SERIAL I/O CONTROL GROUP

binary-coded-decimal number to the 6 and

ASYNCHRONOUS DATA TRANSFER

7 decoder U21 and U51. On the sixth

CONTROL CIRCUIT.

count (0110), the 6 and 7 decoder U21

5 - 5 0 2 . General. The Serial I/O control

and U51 6 output enables gates G5 and G6

group asynchronous data transfer control

and on the seventh count (0111), the 6 and

5-71