Unit13-SerialIO&ADC&DMA-EE357-Nazarian-Fall09

Unit13-SerialIO&ADC&DMA-EE357-Nazarian-Fall0...

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University of Southern California Viterbi School of Engineering EE357 asic Organization of Computer Systems Basic Organization of Computer Systems erial I/O Serial I/O A-to-D Converter DMA References: 1) Textbook 2) Mark Redekopp’s slide series Shahin Nazarian Fall 2009 3) Freescale documents on CF
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RS-232 Serial Operation RS-232 Serial Ports communicate data 1-bit at a time at a certain baud rate (bits per second) Serial Port onnector Control bits (start/stop/parity) are usually included in data stream Full-duplex transmission Tx Connector Transmit and Receive at the same time 2 I/O pins: Tx and Rx alf uplex Rx RTS Half-duplex Only 1 transmitter at a time Example: transmission of 11000011 CTS Start 11000011 Stop Shahin Nazarian/EE357/Fall 2009 2 Baud Period
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[Optional] RS232 Pins Pin Number Direction of signal 1 Carrier Detect (CD) (from DCE) Incoming signal from a modem 2 Received Data (Rx) Incoming Data from a DCE 3 Transmitted Data (Tx) Outgoing Data to a DCE () gg 4 Data Terminal Ready (DTR) Outgoing handshaking signal ignal Ground Common reference voltage 5 Signal Ground Common reference voltage 6 Data Set Ready (DSR) Incoming handshaking signal 7 Request To Send (RTS) Outgoing flow control signal 8 Clear To Send (CTS) Incoming flow control signal Shahin Nazarian/EE357/Fall 2009 9 Ring Indicator (RI) (from DCE) Incoming signal from a modem
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[Optional] DCE and DTE DTE stands for Data Terminal Equipment, and DCE stands for Data Communications Equipment These terms are used to indicate the pin-out for the connectors on a device and the direction of the signals on the pins Your computer is a DTE device, while most other evices are usually DCE devices devices are usually DCE devices For more details on serial communication terms and acronyms you may refer to: http://www.taltech.com/resources/intro-sc.html#dce Shahin Nazarian/EE357/Fall 2009
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Establishing Serial Connections • Both devices must be configured for the same settings to be able to communicate data correctly our case we will be communicating with a PC In our case, we will be communicating with a PC running a serial terminal program that allows us to configure our settings • We will normally use a baud rate of 19200, 8 data bits, no parity bits , 1 stop bit, and no flow control S 32 Serial erial settings controlled RS-232 Serial Shahin Nazarian/EE357/Fall 2009 5 Serial settings controlled by configuration registers
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Error Checking & Flow Control Error-checking ensures that the data the receiver thinks it got is what the transmitter thinks it sent A bit may get flipped or synchronization may be lost and bits are misinterpreted Adding a parity bit allows us to detect an error (but not correct it) and ask the transmitter to re-send the data Even (odd) Parity idea: Always have an even (odd) number of 1’s in the transmission. The parity bit is whatever value needed for an even dd) of 1’s is needed for an even (odd) of s Flow control ensures that the receiver can keep up with the transmission rate of the transmitter
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Unit13-SerialIO&ADC&DMA-EE357-Nazarian-Fall0...

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