MA28151 datasheet(9/22 Pages) DYNEX

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MA28151

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3.10 COMMAND INSTRUCTION DEFINITION

Once the functional definition of the MA28151 has been

programmed by the Mode Instruction and the sync characters

are loaded (if in Sync Mode) then the device is ready to be

used for data communications. The Command Instruction

controls the actual operation of the selected format. Functions

such as: Enable Transmit/Receive, Error Reset and Modem

Controls are provided by the Command Instruction.

Once the Mode Instruction has been written into the

MA28151 and Sync characters inserted, if necessary, then all

further “control writes” (CDN=1) will load a Command

Instruction. A Reset Operation (internal or external) will return

the MA28151 to the Mode instruction format.

Note: Internal Reset on Power-up. When power is first

applied, the MA28151 may come up in the Mode, Sync

character or Command format. To guarantee that the device is

in the Command instruction format before the Reset command

is issued, it is safest to execute the worst-case initialization

sequence (sync mode with two sync characters). Loading

three 00Hs consecutively into the device with CDN=1

configures sync operation and writes two dummy 00H sync

characters. An internal reset command (40H) may then be

issued to return the device to the idle state.

3.11 COMMAND INSTRUCTION FORMAT

TRANSMIT ENABLE

1 = ENABLE

0 = DISABLE

RTS

SBRK

RxE

DTR

TxEN

DATA TERMINAL READY

HIGH WILL FORCE DTR

OUTPUT TO ZERO

RECEIVE ENABLE

1 = ENABLE

0 = DISABLE

SEND BREAK CHARACTER

1 = FORCES TxD LOW

0 = NORMAL OPERATION

ERROR RESET

1 = RESET ERROR FLAGS

PE, OE, FE

REQUEST TO SEND

HIGH WILL FORCE RTS

OUTPUT TO ZERO

INTERNAL RESET

HIGH RETURNS THE MA28151 TO

MODE INSTRUCTION FORMAT

ENTER HUNT MODE*

HIGH ENABLES SEARCH FOR SYNC

CHARACTERS (HAS NO EFFECT IN ASYNC MODE)

*NOTE: ERROR RESET must be performed whenever RxENABLE and ENTER-HUNT

are programmed.

Figure 12: Command Instruction Format

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