【正文】 consists of an IBM PC ATclass puter connected to a Hayespatible, Prometheus 1200 baud modem. The modem was selected because it was inexpensive and available. A faster modem may be used if desired, although once the file transmission time is reduced below one minute, further reductions in transmission time do not further reduce connect time charges. A possible advantage to higher transmission speeds is the automatic error detection and correction available in some high speed modems. Prom Plus version , a mercial data munications package, is used to configure the modem, set up munications parameters, and establish a link with the remote modem. Prom Plus includes a macro language called ASPECT, which allows the user to write and pile scripts which implement c ustom file transfer protocols. A simple ASPECT script was written to read the contents of a program file and upload it to the remote programmer. The file transfer protocol (FTP) implemented is a simple sendandwait, packetoriented protocol. The trans mit and receive modes of the FTP are illustrated by the flowcharts in figures 4 and 5, respectively. The transmitter sends each packet without flow control and waits for a response. The programmer (the receiver) reads and dissects the packet while calculating a checksum. If the calculated checksum is valid, the programmer acknowledges the packet by sending an ACK. If the checksum is in error, the programmer negatively acknowledges the packet by sending a NAK. Upon receipt of an ACK, the transmitter sends the next packet. If the transmitter receives a NAK, it resends the same packet. Transmission proceeds in this manner until the entire file has been transferred. The programmer might respond to a packet by sending a CAN, which indicates that a nonrecoverable error has occurred and that the transmitter should immediately abort the file transfer. If the programmer fails to respond to a packet within a limited period of time, the transmitter will resend the same packet. The transmitter will continue to resend the same packet until a valid response is received or until the allowed number of attempts is exceeded, at which time the file transfer is aborted. After each packet is received and validated by the programmer, the data contained in the packet is programmed into the AT89C51 controller in the application. After programming, the data is read back from the controller and verified against the received packet data. Successful verification indicates successful programming, causing the programmer to send ACK to the transmitter. If programming fails, the programmer sends CAN to signal the transmitter to abort the file transfer. The simplicity of the FTP reduces the amount of AT89C51 program memory used in the programmer. The sendand wait nature of the FTP allows interpacket delays due to AT89C51 program and erase times to be easily absorbed. Support for program verification is transparent, requiring no explicit mand or result codes, or additional data transfers. The files which are uploaded to the programmer are created with the tools in the Intel MCS51 Software Development Package for the IBM PC. Included in the package are the MCS51 Macro Assembler, MCS51 Relocator and Linker, and a useful utility, OH. OH converts an absolute 8051 object file to an equivalent ASCII hexadecimal object file. The records in the hex file produced by the OH utility serve, unchanged, as the packets in the FTP described above。該應用 指南 所描述的電路只支持 5v 電壓下編程。應用程序使用的外部程序存儲器要求這一腳為低電平才能正常運行。 ALE/ PROG 在編程過程中輸出低電平，在正常運行期間絕不能使用。帶有三個輸出狀態(tài)的緩沖區(qū)會在應用程序之間插入電路和控制器，同時 在編程時緩沖區(qū)輸出三種狀態(tài)。鎖存在編程期間是可用的，并保存應用程序的電路狀態(tài)。在第一種模式的時候，進入一個字符從右邊顯示和快速移動，通過每個元素顯示其在最后的裝配位置的左側。這就產生了 16 名顯示元素，每個數(shù)字有 09 的顯示能力，是大寫字母， 標點符號和一些字符。 支持應用程序的修改 。在基本應用時未使用的 PSEN 和 ALE/ PROG，是被程序員直接控制的。 請注意，加在開關上的四個電阻在基本應用中并不是必須的，因為 AT89C51的端口上提供一個內部上拉電阻。 透明鎖存器被加在了控制器的兩個端口之間做輸入控制。在編程過程中，復位鍵生效，多路開關信號輸入，以及凍結顯示鎖存控制線。由于顯示控制輸入不為高電平，直到新的程序寫 入顯示器內部不被打亂。該控制器運行在 兆 赫茲 ，此頻率允許串口運行在一個標準波特率下。 AT89C51 的端口 1， 2， 3內部有大約 3000 歐姆的上拉電阻，因為端口 0 沒有內部上拉電阻，所以外部 10千歐姆的上拉電阻已經加上 并 允許適當?shù)某绦蛘J證模式操作。這就要求程序代碼和 I / O 緩沖區(qū)保持足夠小以適合片上存儲器。當編程完成后，應用程序執(zhí)行新的程序，它顯示新信息。更高的傳輸速度的可能優(yōu)勢是在某些高速調制解調器內的自動錯誤檢測和糾正。 文件傳輸協(xié)議（ FTP）的實施，是一個簡單的發(fā)送和等 待的，數(shù)據(jù)包導向的協(xié)議。如果計算 出的校驗和是有效的，程序員通過發(fā)送一個 ACK 承認此數(shù)據(jù)包。以這種方式傳輸，直到整個文件已被移交。每個數(shù)據(jù)包接收和通過程序員驗證后，數(shù)據(jù)包中包含的數(shù)據(jù)被加載到的 AT89C51 單片機控制器編程。 簡單的 FTP 減少了 AT89C51 的程序在編程時使用的內存量。在包中包括了 MCS 51 宏匯編， MCS 51 單片機 Relocator 和連接器，以及一個有用的工具， OH。 通話被檢測到并連接建立后，程序器強迫暫停其程序的執(zhí)行。在配置調制解調器接聽來電后，程序控制器停止工作。 串行接口，程序員通過它連接到調制解調器，它支持兩個握手信號， DTR 和 DSR。當檢測到輸入，調制解調器響應并試圖與輸入建 立通信。如果來電掛斷，在得到下一次呼叫之前，三十秒時間必須終止。 兩個數(shù) 據(jù)包類型定義：數(shù)據(jù)和最終文件。末端文件包中包含與數(shù)據(jù)包相同的領域的文件，但該數(shù)據(jù)字段是空的。編程器給傳送者發(fā)送一個 NAK 作為信號數(shù)據(jù)包的接收和恢復為一個有效的數(shù)據(jù)包報頭審查的警示信號。然后編程器在程序模式中放置控制器。由于 30 秒的復位延遲，編程器重新對有效的數(shù)據(jù)包報頭進行測試。 重要的是要注意，無效的數(shù)據(jù)包永遠不會規(guī)劃到應用程序控制器。 如果一個有效的數(shù)據(jù)包在 30 秒延遲之前接收，另一個只能被接受一個有效的末端文件而終止的程序循環(huán)開始執(zhí)行。 。在這種情況下應用控制器被保留在程序設計模式，以防止它執(zhí)行這個程序。 根據(jù)末端文件的接收，編程器向閑置的狀態(tài)電源返回其控制輸出，允許應用程序控制器，開始執(zhí)行新的程序。調制解調器掉線，程序器繼續(xù)休眠等待下一次呼叫。編程后，從控制器內將數(shù)據(jù)讀回并與接收到的數(shù)據(jù)包中的數(shù)據(jù)進行比較。該控制器的中斷響應放棄其正在運行的程序，并顯示一條消息，表明程序已經被替代。 任何包含有效文種的數(shù)據(jù)包，記錄長度或校驗和無效。數(shù)據(jù)字段包含程序的數(shù)據(jù)在應用程