RC8650 datasheet(9/48 Pages) ETC

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RC8650 VOICE SYNTHESIZER

RC SYSTEMS

Figure 1.3. RS-232C Interface

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Table 1.2. Baud Rate Options

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High or Low period detected in the input stream. This period is as-

sumed to be the bit rate of the incoming data. In addition to the baud

rates listed in Table 1.2, auto-detect mode also supports 38400,

57600, and 115200 baud rates.

In order for the RC8650 to determine the incoming baud rate, there

must be at least one isolated “1” or “0” in the input character. The CR

character, 0Dh, is recommended for locking the baud rate. The char-

acter is not otherwise processed by the RC8650; it is discarded.

If the measured bit period is determined to be a valid baud rate, the

RC8650 acknowledges lock acquisition by transmitting the ASCII char-

acter “l” (6Ch) on the TXD pin. The baud rate will remain locked unless

changed with the baud rate command, or the RC8650 is reset.

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Figure 1.4. Baud Rate DetectionTiming

INTERFACING THE RC8650

The RC8650 contains both asynchronous serial and 8 bit bus interfac-

es. All text, commands, tone generator data, real time audio data, etc.,

are transmitted to the RC8650 via one of these ports. For maximum

ﬂexibility, use of the serial port is recommended whenever possible.

Not all RC8650 functions are supported through the bus interface. In

particular, index markers, operating system updates, chipset identiﬁ-

cation, current operating settings, and A/D conversion are only sup-

ported through the serial interface.

Serial Interface

The serial port operates with 8 data bits (LSB ﬁrst), 1 or more stop bits,

no parity, and any standard baud rate between 300 and 115200 bps.

A typical RS-232C interface is shown in Figure 1.3. Note that the

MAX232A transceiver is not required if the host system’s serial port

operates at logic levels compatible with the RC8650 (0/+5 or 0/+3.3

V). The RC8650’s serial port may be connected directly to the host

system in this case.

The CTS# pin should be used to control the ﬂow of serial data to the

RC8650. It is not necessary to check CTS# before transmitting every

byte, however. All data is routed through a high speed 16-byte buffer

within the RC8650 before being stored in the primary buffer. CTS# may

be checked every eight bytes with no risk of data loss.

Baudrateselection

The serial port’s baud rate can be programmed using any of three

methods: pin strapping, auto-detect, and by command. Pin strapping

sets the baud rate according to the logic levels present on the BRS0–

BRS2 pins, as shown in Table 1.2. Auto-detect enables the serial port

to automatically detect the baud rate of the incoming data. The baud

rate command (described in Section 2) allows the baud rate to be

changed at any time, effectively overriding the ﬁrst two methods. Pin

strapping cannot be used to program baud rates higher than 19200; to

do this, auto-detection or the baud rate command must be used.

The automatic baud rate detection mechanism is enabled when the

BRS0–BRS2 pins are all at a High logic level and the BRD pin is con-

nected to the RXD pin. The baud rate is determined by the shortest

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