keydown event new value

Navegador: Google Chrome V19.0.1084.52

Eu tenho uma caixa de texto que precisa ser um número menor ou igual a 255, no keydown eu quero verificar se este valor é superior ou igual a 255 mais impedir o evento.

No console quando eu console.log oevento vai mostrarevent.srcElement.value como o valor aparecerá, por exemplo, de 12 => 123, quando eu console.log apenasevent.srcElement.value mostrará como a entrada foi, não será.

Console.log está acontecendo um após o outro, nada no meio, sem pausas.

Como posso encontrar o que o novo valor de uma caixa de texto estará no keydown e por que o console.log está retornando resultados diferentes?

obrigado

Aqui está meu código:

function inputNumeric(event,max) {

    console.log (event);
    console.log ('event.originalEvent.srcElement.value: '+event.originalEvent.srcElement.value);
    console.log ('event.srcElement.value: '+event.srcElement.value);

}

$("#rs485addr").keydown(function(event) {
    inputNumeric(event);
});

Console.log:

event.originalEvent.srcElement.value: 12
event.srcElement.value: 12

event.srcElement:

accept: ""
accessKey: ""
align: ""
alt: ""
attributes: NamedNodeMap
autocomplete: ""
autofocus: false
baseURI: "http://10.50.50.60/controller/?bid=10"
checked: false
childElementCount: 0
childNodes: NodeList[0]
children: HTMLCollection[0]
classList: DOMTokenList
className: "width-60"
clientHeight: 18
clientLeft: 2
clientTop: 2
clientWidth: 62
contentEditable: "inherit"
dataset: DOMStringMap
defaultChecked: false
defaultValue: "1"
dir: ""
dirName: ""
disabled: false
draggable: false
files: null
firstChild: null
firstElementChild: null
form: null
formAction: ""
formEnctype: "application/x-www-form-urlencoded"
formMethod: "get"
formNoValidate: false
formTarget: ""
hidden: false
id: "rs485addr"
incremental: false
indeterminate: false
innerHTML: ""
innerText: ""
isContentEditable: false
jQuery17102950612970162183: 22
labels: NodeList[1]
lang: ""
lastChild: null
lastElementChild: null
localName: "input"
max: ""
maxLength: 3
min: ""
multiple: false
name: ""
namespaceURI: "http://www.w3.org/1999/xhtml"
nextElementSibling: null
nextSibling: Text
nodeName: "INPUT"
nodeType: 1
nodeValue: null
offsetHeight: 22
offsetLeft: 183
offsetParent: HTMLBodyElement
offsetTop: 365
offsetWidth: 66
onabort: null
onbeforecopy: null
onbeforecut: null
onbeforepaste: null
onblur: null
onchange: null
onclick: null
oncontextmenu: null
oncopy: null
oncut: null
ondblclick: null
ondrag: null
ondragend: null
ondragenter: null
ondragleave: null
ondragover: null
ondragstart: null
ondrop: null
onerror: null
onfocus: null
oninput: null
oninvalid: null
onkeydown: null
onkeypress: null
onkeyup: null
onload: null
onmousedown: null
onmousemove: null
onmouseout: null
onmouseover: null
onmouseup: null
onmousewheel: null
onpaste: null
onreset: null
onscroll: null
onsearch: null
onselect: null
onselectstart: null
onsubmit: null
onwebkitfullscreenchange: null
onwebkitfullscreenerror: null
onwebkitspeechchange: null
outerHTML: "<input class="width-60" id="rs485addr" maxlength="3" type="textbox" value="1">"
outerText: ""
ownerDocument: HTMLDocument
parentElement: HTMLSpanElement
parentNode: HTMLSpanElement
pattern: ""
placeholder: ""
prefix: null
previousElementSibling: HTMLLabelElement
previousSibling: Text
readOnly: false
required: false
scrollHeight: 16
scrollLeft: 0
scrollTop: 0
scrollWidth: 60
selectionDirection: "forward"
selectionEnd: 3
selectionStart: 3
size: 20
spellcheck: true
src: ""
step: ""
style: CSSStyleDeclaration
tabIndex: 0
tagName: "INPUT"
textContent: ""
title: ""
translate: true
type: "text"
useMap: ""
validationMessage: ""
validity: ValidityState
value: "123"
valueAsDate: null
valueAsNumber: NaN
webkitGrammar: false
webkitRegionOverflow: "undefined"
webkitSpeech: false
webkitdirectory: false
webkitdropzone: ""
willValidate: true

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