ece3803_d2008_hw4_solutions

ece3803_d2008_hw4_solutions - ECE 3803 D2008 Homework 4...

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ECE 3803 D2008 Homework 4 solutions 1 ECE 3803 D2008: Microprocessor System Design Homework 4 solutions I/O ports with handshaking 1. [40 pts] Design a simple 8-bit parallel communication link between two AT91M42800A systems (using the external bus interface). This is a unidirectional link: one system transmits, the other receives; one byte at a time. It is suggested that a handshaking flag be used, readable by both sides. Writing the transmit port should automatically set the handshaking flag, and reading the receive port (on the other system) should automatically clear the flag. a) [25 pts] Draw schematics of the relevant I/O hardware for each side, excluding the details of address decoders. D0 D1 D2 D3 D4 D5 D6 D7 NWR0 NRD OE 1 CLK 11 1D 2 1Q 19 2D 3 2Q 18 3D 4 3Q 17 4D 5 4Q 16 5D 6 5Q 15 6D 7 6Q 14 7D 8 7Q 13 8D 9 8Q 12 U2 74AHC574 OE 1 LE 11 1D 2 1Q 19 2D 3 2Q 18 3D 4 3Q 17 4D 5 4Q 16 5D 6 5Q 15 6D 7 6Q 14 7D 8 7Q 13 8D 9 8Q 12 U4 74AHC573 D0 D1 D2 D3 D4 D5 D6 D7 D 2 Q 5 Q 6 CLK 3 4 1 PRE CLR U3A 74AHC74 CS(Tx_port) CS(status_port) VDDIO VDDIO 1 2 3 U5A 74AHC00 Handshake_flag Handshake_clear D0 D1 D2 D3 D4 D5 D6 D7 NRD NRD OE 1 LE 11 1D 2 1Q 19 2D 3 2Q 18 3D 4 3Q 17 4D 5 4Q 16 5D 6 5Q 15 6D 7 6Q 14 7D 8 7Q 13 8D 9 8Q 12 U5 74AHC573 D0 D1 D2 D3 D4 D5 D6 D7 CS(Rx_port) CS(status_port) Handshake_flag OE 1 LE 11 1D 2 1Q 19 2D 3 2Q 18 3D 4 3Q 17 4D 5 4Q 16 5D 6 5Q 15 6D 7 6Q 14 7D 8 7Q 13 8D 9 8Q 12 U6 74AHC573 link_data0 link_GND System 1 System 2 link_data1 link_data2 link_data3 link_data4 link_data5 link_data6 link_data7 R1 10k VDDIO R1 10k 1 2 3 U1A 74AHC32 4 5 6 U1B 74AHC32 1 2 3 U7A 74AHC32 4 5 6 U7B 74AHC32 The pull-up/pull-down resistors make sure that if the link is disconnected, System 2 will never see the handshake flag set to 1 (indicating data is ready to be received), and
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ece3803_d2008_hw4_solutions - ECE 3803 D2008 Homework 4...

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