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问候语!我想使用外部并行RAM与PIC32 MX450F128H。问题是这个控制器只有14个PMA引脚,但RAM芯片有17个地址引脚(IS62WV128BLL)。我想达到这个RAM的高速访问。那控制器是可能的还是我必须使用另一个控制器?我即将在高速的UART接口上接收大量的数据,我希望能够访问这个外部RAM,这样我就可以在里面写入收入数据并阅读它。我确信我可以用普通的PIN来完成这项任务,但是我会从访问速度中损失多少呢?谢谢!
以上来自于百度翻译 以下为原文 Greetings! I want to use external parallel RAM with PIC32MX450F128H. The problem is this controller has only 14 PMA pins, but the ram chip has 17 address pins(IS62WV1288BLL). I want to reach high speed access to this RAM. Is that possible with that controller or I have to use another one? I`m about to receive huge amounts of data on UART interface on high speed and I want to be able to access this external ram, so I can Write income data in it and read it. I`m sure I can do this using usual pins, but how much I`m about to lose from the access speed? Thanks! |
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9个回答
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从来没有在PIC32上使用PMP,但是我可以从文档中看到,这和我使用的PIC24类似:所以,你有多达16位的地址线和8条或16条数据线:这使得最大128KB…因为这个PIC有128KB的RAM,我不确定你会从中得到很大的帮助。访问软件中的外部RAM将明显慢,如(大约)100NS而不是20:点是,你需要多快?一个大的SPI RAM怎么样?
以上来自于百度翻译 以下为原文 Never used PMP on a PIC32 but I can see from the docs that this is similar to the PIC24 I used: so, well, you have up to 16bits of address lines and 8 or 16 data lines: which makes some maximum 128KB... Since this PIC has 128KB of RAM, I am not sure you will get a big help from that. Accessing an external RAM in software will be significantly slower, say (roughly) 100nS instead of 20: point is, how fast do you need that to be? How about a larger SPI RAM? |
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不!这个PIC有32 K RAM。我需要一个缓冲器,我想用112500波特率来填写收入数据。我想100纳秒就可以了。如果可能的话,我想写在RAM中的收入数据中断(关于UART)和在主程序中读取和处理它!我不确定PMP能组织这样的访问。我以前还没有使用它。主要目标是UC RAM来免费处理和外部RAM来存储收入数据。这是可以实现的吗?我是否需要使用分离的程序来确保没有同时读写的尝试,或者PMP能为我做到这一点吗?谢谢!
以上来自于百度翻译 以下为原文 No! This PIC has 32k RAM. And I need a buffer which I want to fill with income data on 112500 baud rate. I think 100ns is ok. If it`s possible I want to write to the RAM in the income data interrupt(on UART) and in the main program to read and process it! I`m not sure the PMP can organize such access. I haven`t use it before. The main goal is the uC RAM to stay free for processing and the external ram to store income data. Is this achievable? Do I have to use a separated procedures to ensure no simultaneous read and write attempt or PMP can do this for me? Thanks! |
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哦,你是对的。在同一个家庭里,还有其他MCU可能与64和128KB RAM兼容。我看:那么,如果64K x2字节足够你,你可以使用PMP,否则你必须使用更多的引脚,并在软件中做到这一点。至于“锁定”单个操作,嗯,是的,您应该使用一些机制:PMP可能只需要一个指令,而软件解决方案将占用更多,因此需要一些信号量。
以上来自于百度翻译 以下为原文 Oh you're right - in the same family there are other MCUs possibly pin-compatible with 64 and 128KB RAM. I see then: So, if 64K x 2byte is enough for you, you can use the PMP, otherwise you have to use more pins and do that in software. As for "locking" single operations, well, yes, you should use some mechanism: PMP will possibly only need a single instruction, while a software solution will take more and hence the need for some semaphore. |
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还有一个问题!在没有外部上拉电阻的情况下,我能将SRAM直接连接到控制器吗?我想实现低电磁干扰水平,所以我想把SRAM尽可能接近控制器,并添加-50-100欧姆电阻器至少在较低的地址引脚和所有数据引脚。但是,如果我添加外部拖动,有这么多的组件,我必须把SRAM远离控制器(我将使用0805个电阻)。内部拉力够了吗?你还可以建议我为下埃米斯做些什么呢?我将把100NF旁路盖放在SRAM下面。我需要铁氧体珠吗?谢谢!
以上来自于百度翻译 以下为原文 One more question! Can I connect my SRAM directly to the controller without external pull-up resistors? I want to achieve low EMI levels, so I want to put the SRAM as close as possible to the controller and to add -50-100 ohms resistors at least on the lower address pins and to all data pins. But if I add external pull ups, there are so many components I have to put the SRAM far away from the controller(I`m going to use 0805 resistors). So are the internal pull-ups enough? What else can you advise me to do for lower EMIs? I`ll put 100nF bypass cap beneath the SRAM. Do I need ferrite bead? Thanks! |
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正如我所说的,我在EMI抑制方面请求。我将以非常高的速度访问RAM。我需要大约100NS(芯片是设计为55纳秒,但我给一个小的公差)。这就是为什么我选择了一个并行RAM。我的控制器将接收1MbPUART/RS485接口的数据,我需要在内部RAM过载之前把它存储在某个地方。在这种情况下,你会怎么做?你会直接把RAM连接到控制器上,而不需要在线路上的电阻器上有任何外部的上拉,所以连接尽可能短,或者你要放置很多外部元件来抑制EMI,但是扩大了轨迹和距离?
以上来自于百度翻译 以下为原文 As I said I`m asking in the EMI suppression aspect. I`ll access my ram at very high speed. I need around 100ns(the chip is designed for 55ns, but I`m giving a small tolerance). This is why I`ve chosen a parallel ram. My controller will receive data on 1Mbps UART/RS485 interface and I need to store it somewhere before my internal ram is overloaded. What would you do in this situation? Are you going to connect the ram directly to the controller without any external pull ups on resistors on lines, so the connections to be as short as possible on or you`re going to put a lot of external elements to suppress EMI, but enlarging the traces and distances? |
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是的,我会直接连接它,没有组件添加(除了明显的解耦)和关闭。自从1MbPs的100倍,使100kBys/s,你的100Ns允许10Mb/s -所以,可以容忍,但你很舒服。
以上来自于百度翻译 以下为原文 Yes, I would connect it directly, no component added (apart obvious decoupling) and close. Do consider that your timings are... 100 times off since 1Mbps makes 100Kbytes/sec and your 100nS allow 10Mbytes/sec - so, ok about tolerances, but you're quite comfortable. |
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是的,我知道,但是因为它是GPRS调制解调器的一部分,所以ACK包在线路上有很大的延迟,最大输出包长度大约是1400个值。即使我使用一系列输出包,我也需要一个大缓冲区来存储数据在ACK之间。
以上来自于百度翻译 以下为原文 Yes, I know, but because it`s part of a GPRS modem there is a lot of delay for ACK package on the line and the max output package length is around 1400 value bites max. I have to store that data somewhere and to process the packages. Even I if I use series of output packages I need a big buffer to store the data between the ACKs. |
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好的,我的意思是,你不会有16个或更多的线路振荡在10MHz或更多,而短脉冲约100Ns宽在100,500千赫的速率。我不是EMI的大专家,但这是一个需要考虑的问题(并且应该让生活更容易)。
以上来自于百度翻译 以下为原文 Ok, what I mean is that you won't have 16 or more lines oscillating at 10MHz or more, rather short pulses some 100nS wide at a 100, 500KHz rate. I am not a big expert at EMI but this is something to be taken into account (and should make life easier). |
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