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RC8650L Datasheet(PDF) 10 Page - List of Unclassifed Manufacturers |
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RC8650L Datasheet(HTML) 10 Page - List of Unclassifed Manufacturers |
10 / 48 page 10 RC8650 VOICE SYNTHESIZER RC SYSTEMS Note The measurement cycle ends when there have been no High- to-Low nor Low-to-High transitions on the BRD pin for 75 ms or longer. Consequently, the RC8650 will ignore any data sent to it for a period of 75 ms after the “lock-on” character has been received. The CTS# pin is driven High during this time, and the acknowledgment character is not transmitted until the RC8650 is actually ready to accept data. See Figure 1.4. Statusmessages Real-time status information is provided via the TXD pin. Status are transmitted as one-byte messages, shown in Table 1.3. Each mes- sage correlates to a status flag in the Status Register, shown in Table 1.4. The specific character used, and whether it will be transmitted, are functions of the VC and STM bits of the Protocol Options Register. (The Protocol Options Register is described in Section 2.) For informa- tion about how to obtain reading-progress status, see the Index Marker command description. Table 1.3. Status Messages Because the RC8650 can take up to 15 µs to accept data written to it (AC Characteristics, tYHWH parameter), software drivers should wait for RDY to drop to 0 after a byte is written in order to avoid overwriting it with the next data byte. Not doing so could result in the loss of data. Waiting for RDY to drop to 0 ensures that RDY will not falsely show that the RC8650 is ready the next time the driver is called. If a system interrupt can occur while waiting for RDY to become 0, or if RDY cannot otherwise be checked at least once every 8 µs, a software timeout should be enforced to avoid hanging up in the wait loop. The time RDY stays 0 is relatively short (8 µs min.) and can be missed if in- terrupted. The timeout should be at least 15 µs, which is the maximum time for RDY to drop to 0 after writing a byte of data. In non time-criti- cal applications, the output routine could simply delay 15 µs or longer before exiting, without checking for RDY = 0 at all. Figure 1.5 illustrates the recommended method of writing data to the RC8650’s bus interface. This method should be used for writing all types of data, including text, commands, tone generator and real time audio data. Bus/Printer Interface The RC8650’s bus interface allows the RC8650 to be connected to a microprocessor or microcontroller in the same manner as a static RAM or I/O device, as shown in Figure 1.6. The microprocessor controls all transactions with the RC8650 over the system data bus using the RD and WR# signals. RD controls the reading of the RC8650’s Status Register; WR# controls the transfer of data into the RC8650. The Status Register bits and their definitions are shown in Table 1.4. A registered bus transceiver is required for communication between the RC8650 and microprocessor; two 74HCT374s placed back to back may be substituted for the 74HCT652 shown in the figure. Prior to each write operation to the RC8650, the host processor should verify that the RC8650 is ready by testing the RDY status flag. The RC8650 can also be interfaced to a PC’s printer port as shown in Figure 1.6. A 74HCT374 can be used in place of the 74HCT652, since bidirectional communication is not necessary. Handshaking is performed automatically via the BUSY pin. ����������� �������� �� ��� ������� � ����� ���������� ��������� ����������� �������� �� ��� ������� � �������������� ����� ������� � �� ��� Figure 1.5. Recommended Method ofWriting DataVia the Bus Interface ����� �������� ������� ������������������ ��� ������ ��� ��� ������ ������������������ ��� ��� ��� ������������������� ���������������������� ��� � ��� ������������������ ���������������������� ��� � ��� �������������� ������������ ��� ��� �� ������������ ������������ ��� ��� �� |
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