Abstract: This article introduced the CYPRESS Corporation’s high speed pair of mouth RAM CY7C026 principle of work, as well as it based on DSP the TMS320VC5402 chip’s high speed data gathering aspect’s application, simultaneously discussed CY7C026 to take in the high speed data gathering system’s high speed connection merit.
Key words: CY7C026; DSP; High speed data transmission
Introduction
—The front end data acquisition system which controlled through the PCI main line obtained the widespread application by the industry computer in the industrial control domain, the data transmission system generally will create the data jamming phenomenon in the great data quantity’s situation. Undergoes various comparison in system design’s process, finally used Gao Shushuang the mouth RAM constitution the high speed data exchange connection to solve this problem successfully.
—CY7C026 is CYPRESS Corporation produces 16K×16 high speed pair of mouth static state RAM, the access speed is smaller than 25ns. It has the true twin port, may simultaneously carry on the data access, two ports have the independent control holding wire, the address wire and the data line, moreover through main/may expand the storage capacity and the data width conveniently from the choice. Through the chip signal quantity marker, the left and right two ports may realize chip resources sharing. The CY7C026 chip’s base pin explained that see also Table 1, the internal function diagram see Figure 1.
CY7C026 principle of work
* deposit principle
—May see by the CY7C026 internal structure drawing, this chip’s hard core is the twin port memory array, about two ports may use in common this memory array, and has the respective pilot wire, when deposits and withdraws the data alone, is the same with ordinary RAM. Simultaneously reads when the different storage space the data and simultaneously reads the same data space the data, about the port may also carry on. If simultaneously does to the same data space writes the operation, or a port does to a data space reads the operation at the same time another port to do to this data space writes the operation, about the port will have the conflict. Therefore, CY7C026 processes these two kind of situations through the BUSY base pin.
—When about the port carries on the read-write operation to the different storage space, but simultaneous access. This time, about port’s BUSY signal simultaneously sets high. If simultaneously carries on time the store operation to the identical storage space, which end’s memory requirement signal does appear first, then this end’s BUSY signal sets high, permission memory. Which end’s stored signal does appear, then this carries the BUSY signal to set lowly, forbids to save.
—It is noteworthy that about the both sides deposit request signal appears the time difference must be bigger than 5ns, otherwise which one side is the arbitration logic unable to judge the deposit request signal to appear before. If presents the time difference which the both sides deposit request signal appears is smaller than the 5ns situation, the arbitration logic one side BUSY signal will set high, one side BUSY signal will set in addition lowly, thus guaranteed that two port carries out the data storage, another port carries on the data read, has avoided the conflict.
* look-at-me function and main/from pattern use
—The CY7C026 chip’s look-at-me function passes “the mailbox” to realize. So-called “the mailbox” is refers to the chip to take memory’s high address 3FFF the left port “the mailbox”, but 3FFE takes the right port “the mailbox”. Below take the left port toward right port transmission data as the example, the explanation look-at-me function usage. When the left port reads in the data the right port “the mailbox”, the right port’s INTR base pin will produce the signal of stop, namely the INTR base pin will set lowly. After the right port reads this data, signal of stop automatic reset. The right port toward left port transmission data’s situation and the above situation are the same. What the user need is clear, this function is only suitable for the data low speed transmission.
—Actual, the data width often is bigger than 16. By now needed to expand the data position the width, the CY7C026 M/S base pin has provided the function which the data expands. For example, in the practical application needs 32 data buses frequently, may set lowly a piece of CY7C026 M/S base pin, another piece of M/S base pin sets high, then two chip’s base pins connects in together then.
—High speed data gathering and transmission system diagram
* signal quantity marker use
—The signal quantity marker is the most characterful function which this chip has, uses this kind of function to be possible to realize internal resources sharing. CY7C026 is realizes this function, has provided eight sign latches, each latch corresponds a signal quantity marker. The use signal quantity marker’s process is first sets the SEM base pin lowly, the CE base pin sets high, then chooses the corresponding symbol latch through a0~A2 three address wires, the data deposit through realizes to the I/O0 operation. In the data access process, R/W and the OE use way with deposits and withdraws the ordinary memory’s use way to be the same. On after chip electricity, the left and right port’s marker is at the idling condition. By now about two ports both might through to symbolize willfully the latch writes “0″ proposed uses this signal quantity marker the request. Then reads this signal quantity marker the value to determine whether to obtain the right of use, if reads the value is “0″, then explained that this port obtains the right of use, is “1″, then explained that another port has obtained this marker right of use. Obtains the right of use the port only then after its to use the symbol latch which writes “1″, can give up this signal quantity marker the right of use. If another port gave up the right of use in it before had proposed used this signal quantity marker the request, then after the current port gave up the right of use, another port obtained this signal quantity marker immediately the right of use. On the contrary, if another port has not proposed the request, then this signal quantity marker is at the idling condition.
CY7C026 in data transmission system’s application
—Designs the system is a petroleum oil well logging equipment’s sub-system, the system by the TMS320C5402 primarily processor, takes data sharing through pair of mouth RAM CY7C026 the connection. Its major function is receives the industry computer to read in pair of mouth RAM through the CPCI connection the order, DSP after-crops this order to the mine shaft instrument, after the corresponding mine shaft instrument receives the order, the gathering mine shaft data, then the data transfer to DSP, after undergoing the DSP processing the data reads in pair of mouth RAM. Finally, the industry computer in the pair of mouth RAM will make demonstration processing through the CPCI connection data transfer to the computer. System diagram as shown in Figure 2.
Concluding remark
—Can satisfy the high speed data transmission using the pair of mouth RAM CY7C026 high speed data through-put capacity and the DSP TMS320VC5402 high speed performance the request, simultaneously can complete the massive complex data processing work, thus has given dual attention to the great volume of goods handled which and high speed data transmission processing needs.
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