lpc21isp: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/lpc21isp - from package: lpc21isp

You may install the required package with command apt-get install {package}

Error in other languages:
lpc21isp: bevel nie gevind nie
lpc21isp: comandă negăsită
lpc21isp: comando não encontrado
lpc21isp: commande introuvable
lpc21isp: command not found
lpc21isp: käsku ei ole
lpc21isp: không tìm thấy lệnh
lpc21isp: komanda nerasta
lpc21isp: Kommando nicht gefunden.
lpc21isp: kommandot finns inte
lpc21isp: komut yok
lpc21isp: nie znaleziono polecenia
lpc21isp: níor aimsíodh an t-ordú
lpc21isp: no se encontró la orden
lpc21isp: no s'ha trobat l'ordre
lpc21isp: opdracht niet gevonden
lpc21isp: parancs nem található
lpc21isp: perintah tidak ditemukan
lpc21isp: príkaz nenájdený
lpc21isp: příkaz nenalezen
lpc21isp: команда не найдена
lpc21isp: командата не е открита
lpc21isp: 命令找不到
lpc21isp: コマンドが見つかりません