Intel IXP46X 3.4UART Interface, 3.3.7SRAM Interface, 3.3.8Design Notes, BitDevice, Byte Access

Intel® IXP45X and Intel® IXP46X Product Line of Network Processors—General Hardware Design Considerations

3.3.7SRAM Interface

A typical connection between an 8-bit SRAM memory device and the IXP45X/IXP46X network processors expansion bus is shown in Figure 6 on page 28. When attempting to communicate to this device, the Timing and Control Register for Chip Select must be configured for proper access. For more information, see the Intel® IXP45X and Intel® IXP46X Product Line of Network Processors Developer’s Manual.

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Figure 6. Expansion Bus SRAM Interface

EX_DATA[31:0]	EX_DATA[7:0]	DATA[7:0]
Intel® IXP46X			8-Bit Device
Product Line of
Network Processors	EX_ADDR[18:0]		Byte Access
EX_ADDR[24:0]		ADDR[18:0]
EX_CS_N	CS	E#
EX_RD_N	OE	G#
EX_WR_N	WR	W#	512 Kbyte-x-8
			SRAM
			Interface
			B 4098-003

3.3.8Design Notes

Care must be taken when loading the bus with too many devices. As more devices are added, the loading capacity adds up — to the point where timing can become critical.

To account for this, timing on the expansion bus may be adjusted in the Timing and Control Register for Chip Select. If an edge rises slowly due to low drive strength, the processors should wait an extra cycle before the value is read. For more information, see the documentation on Timing and Control Register for Chip Select bits [29:16] in the Intel® IXP45X and Intel® IXP46X Product Line of Network Processors Developer’s Manual.

3.4UART Interface

The IXP45X/IXP46X network processors provide two dedicated, Universal Asynchronous Receiver/Transmitter Serial Ports (UARTs). These are high-speed UARTs, capable of supporting baud rates from 1,200 Baud to 921.6 KBaud.

The hardware supports a four-wire interface:

•Transmit Data

•Receive Data

•Request to Send

•Clear to Send

Intel® IXP45X and Intel® IXP46X Product Line of Network Processors
HDD	February 2007
28	Document Number: 305261; Revision: 004