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ST16C580CJ44 数据表(PDF) 10 Page - Exar Corporation |
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ST16C580CJ44 数据表(HTML) 10 Page - Exar Corporation |
10 / 41 page ST16C580 10 Rev. 1.20 FIFO Operation The 16 byte transmit and receive data FIFO’s are enabled by the FIFO Control Register (FCR) bit-0. With 16C550 devices, the user can set the receive trigger level but not the transmit trigger level. The 580 provides independent trigger levels for both receiver and transmitter. To remain compatible with ST16C550, the transmit interrupt trigger level is set to 1 following a reset. It should be noted that the user can set the transmit trigger levels by writing to the FCR register, but activation will not take place until EFR bit- 4 is set to a logic 1. The receiver FIFO section includes a time-out function to ensure data is delivered to the external CPU. An interrupt is generated whenever the Receive Holding Register (RHR) has not been read following the loading of a character or the receive trigger level has not been reached. (see hardware flow control for a description of this timing). Hardware Flow Control When automatic hardware flow control is enabled, the 580 monitors the -CTS pin for a remote buffer overflow indication and controls the -RTS pin for local buffer overflows. Automatic hardware flow control is se- lected by setting bits 6 (RTS) and 7 (CTS) of the EFR register to a logic 1. If -CTS transitions from a logic 0 to a logic 1 indicating a flow control request, ISR bit- 5 will be set to a logic 1 (if enabled via IER bit 6-7), and the 580 will suspend TX transmissions as soon as the stop bit of the character in process is shifted out. Transmission is resumed after the -CTS input returns to a logic 0, indicating more data may be sent. With the Auto RTS function enabled, an interrupt is generated when the receive FIFO reaches the pro- grammed trigger level. The -RTS pin will not be forced to a logic 1 (RTS Off), until the receive FIFO reaches the next trigger level. However, the -RTS pin will return to a logic 0 after the data buffer (FIFO) is unloaded to the next trigger level below the pro- grammed trigger level. However, under the above described conditions the 580 will continue to accept data until the receive FIFO is full. Selected INT -RTS -RTS Trigger Pin Logic “1” Logic “0” Level Activation (characters) (characters) (characters) 1 140 4 481 88 14 4 14 14 14 8 |
类似零件编号 - ST16C580CJ44 |
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类似说明 - ST16C580CJ44 |
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