Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. [...]... its parallel- port circuits Although all parallel ports have the same 17 bits, the bits can differ in characteristics such as output impedance and noise immunity Although every parallel port' s outputs should have at least the same current-sourcing and sinking ability as the Parallel Port Complete 10 5 Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Chapter 6 original port, ... includes tips on designing circuits that connect to the parallel port, and on choosing cables to connect the circuits There's also a section on how and when you can use the parallel port as a power source for low-power devices Many parallel ports use ordinary TTL logic, or at best bus drivers and buffers, as the cable interface On the original parallel port, a 74LS374 flip-flop drove the eight Data lines,... CONNECTOR PARALLEL PORT EXPANSION CARD (COMPONENT SIDE( SDS A31 A4 AI nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn IOCATION OF SDS ON FDGF I CONNECTOR Figure 5-8: On many older parallel ports, you can make the Data port bidirectional by cutting one connection and adding a jumper wire On most true bidirectional ports, you don't have to worry about whether the Data port is input or output You can just read the port and... Control bit 5 Reading the bit on a modified port returns a 1 This means that if you read the Control port, then write the same value back to the port, bit 5 will be set to 1, which disables the Data outputs A program that writes to the Control port of a modified port should always write 0 to Control bit 5 if the Data port is being used for output If the Data port is being used for input, the program... shows the relevant parts in the design of a typical early parallel port Not shown are the Control and Status port' s input buffers or the address-decoding and other control signals Lines SDO-SD7 on the expansion bus carry Data bits DO-D7 On the parallel- port card, a 74LS245 octal transceiver buffers ADO-AD7 The lines that connect to Parallel Port Complete Please purchase PDF Split-Merge on www.verypdf.com... Chapter 6 original port, some ports do have weaker drivers A symptom of weak drivers is when a port works only with short cables, or at low speeds Some very low-power devices that connect to the parallel port don't use an external power supply, and draw their current from the port' s outputs, and these devices may not work with weak ports The outputs of many of the newer port controllers meet the improved... use the numbering 1 through 8 for sets of eight bits, but the parallel port' s Data and Control bits and the buffered data bus are numbered beginning with 0.) When the CPU writes to the Data port, BDO-BD7 drive the inputs of a 74LS374 octal flip-flop The outputs of the flip-flops connect through 30-ohm resistors to DCO-DC7 on the parallel- port connector These lines also connect to the inputs of a 74LS244... improved Level 2 interface described in IEEE 1284 These ports can use cables of over 30 feet, if they connect to another Leve12 device Drivers and Receivers The IEEE 1284 standard specifies characteristics for parallel- port drivers and receivers It describes two types of devices: Level 1 devices are similar to the design of the original parallel port, while Leve12 devices give better performance while... 74LS374 and you're done Reinstall the port card and you're ready to test it (Chapter 4 has a bidirectional-test program.) Note that the Data outputs of this port are the totem-pole outputs of a 74LS374 If you intend to use the Data port for input, you must disable the Data outputs before you connect external outputs to the Data lines Otherwise, you risk damaging the port circuits To protect the outputs,... link's performance at high speeds, however Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Chapter 5 104 Parallel Port Complete Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark Interfacing 6 Interfacing Because parallel- port signals may travel over cables of ten feet or more, the cable's design and the circuits that interface to the cable can mean