DP8344 datasheet(183/184 Pages) NSC

183 / 184 page

60 Reference Section (Continued)

line hold

The act of driving the transmission line during

5250

transmissions at the end of a message to allow the

receivers to unsync This insures that the receivers will not

see line noise as the start of another frame when the line

floats

line interface

All the circuity between the BCP and the

communications cable medium

line reflection

Energy from a transmission that is not ab-

sorbed by a load impedance and can cause interference in

that signal

Manchester II encoding

See bi-phase encoding

mask

(1) A mechanism that allows the program to specify

whether interrupts will be accepted by the CPU (2) To dis-

able the accepting of an interrupt by the CPU

mid-bit

In bi-phase encoding the transition in the center

of a bit time

mini-code violation

A violation of the bi-phase encoding

format that is part of the ending sequence in 3270 3299

and the general purpose 8-bit mode The mini-code viola-

tion has no mid-bit transition being high for the entire bit

time There is no mini-code violation in 5250

multidrop

A communication method where all the slave

devices are attached to the same cable and respond to

controller

commands and data only when their own ad-

dress frame precedes the transmitted frame

multi-frame message

Several bytes of data together in

the same uninterrupted message that have only one start

sequence

and one ending sequence

multiplexer

A device that receives 3299 protocol trans-

missions from a controller strips off the address field and

determines over which of eight ports to transmit the mes-

sage in 3270 format The device then directs the response

from the terminal back to the controller

non-promiscuous

A receiver mode that only enables a

data available interrupt when the address frame of the mes-

sage matches that previously specified The 5250 and gen-

eral purpose 8-bit modes

of the BCP support both pro-

miscuous

and non-promiscuous modes

NRZ

Non Return to Zero A data format that uses a high

level to represent a data 1 and a low level to represent a

data 0 The signal level does not return to a zero level in

each bit time See also NRZI

NRZI

Non Return to Zero Inverted A data format similar

to NRZ but with the signal levels reversed

OCLK

The external Oscillator CLocK connected to the

BCP

This frequency from a crystal or a clock cannot be

changed by the BCP itself CPU-CLK is derived from OCLK

in addition the transceiver can be configured so that TCLK

is derived from OCLK

parity

A one bit code usually following data that makes

the total number of 1’s in a data word odd or even including

the parity bit itself It is included as an error checking mech-

anism

POLL

A command issued by a controller to determine

changes in terminal status such as keyboard activity or key-

lock

POLLACK (PACK)

A command issued by a controller

to indicate to the terminal that the controller has recognized

the non-zero status response of the terminal to its POLL

hence its full name pollacknowledge

pop

To remove data from a stack

predistortion

The initial voltage step in a Manchester

encoded

bit used to change frequency components of the

signal to limit introducing jitter

promiscuous

A receiver mode that enables a data avail-

able interrupt regardless of the contents of the transmission

address frame

The 5250 and general purpose 8-bit

modes of the BCP support both promiscuous and non-pro-

miscuous

modes

push

To place data onto a stack

quiesce pulse

A bi-phase 1 bit that is placed at the be-

ginning of a transmission to charge the cable in preparation

for the transmission of data In addition the quiesce pulses

are used as part of the identifying start sequence Typical-

ly five quiesce pulses are placed there

An addressing method that

uses only operands contained in registers

An instruction ad-

dressing mode that adds the unsigned 8-bit value in the

current accumulator to any one of the index registers form-

ing a data memory address for one of the instruction’s oper-

ands

remote access

An access to dual port memory by a

device other than the BCP

repeater

A device used to extend the communication dis-

tance between a controller and a slave device by receiving

the message and re-transmitting it

RIAS

The Remote Interface and Arbitration System that

allows a remote processor and the BCP to share the same

memory with arbitration of any conflict while the BCP is run-

ning A remote processor may also stop and start the BCP

as well as read and write the Program Counter

soft-loadable

A feature of a processor system that allows

another processor to provide it with instructions and data

stack

See LIFO

start sequence

A unique arrangement of bits that begin

each transmission to ensure proper frame alignment and

synchronization Each transmission begins with five bi-

phase

encoded 1’s quiesce pulses a code violation and

the sync bit of the first frame

station address

The identification number of a 5250 ter-

minal or other slave device that will specify which device on

a multidrop line a message is sent to

sync bit

A bi-phase 1 that is placed as the first bit of a

frame

T-state

The period of CPU-CLK

TCLK

The Transceiver CLocK that runs both the transmit-

ter and receiver at a frequency equal to eight times the re-

quired serial data rate The clock can be obtained from a

scaled OCLK or from X-TCLK

time-out

An interrupt that occurs when the timer reaches

a count of zero

transceiver

The TRANSmitter used for sending mes-

sages and the reCEIVER used for reading messages

transformer coupled

The isolation of the transceiver

from the transmission cable through the use of a transform-

er Contrast this with direct coupled

trap

A BCP instruction that forces a software interrupt

183

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