SL8X371 8-Bit Latched Bidirectional I/O Port Legacy Device: Philips/Signetics S8X371 DESCRIPTION The 8X371 I/O Port is a bidirectional device designed for use as an interface element in systems that use TTL-compatible busses. Typically, the 8X371 is used with the 8X305 Microcontroller and its associated interface Vector (IV) bus; however, it can also be used with the 8X300 Microcontroller or an equivalent microprocessor. The 8X371 is functionally the same and pin-for pin compatible with the older 8T31/8X31 but features improved performance and increased drive current. As shown in the logic diagram of Figure 1, the 8X371 consists of eight identical data latches — bits 0 through 7. The latches are accessed from either of two 8-bit busses — the Microcontroller (IV bus) and the user data (UD bus). Separate controls are provided for each bus and both busses operate independently, except when both attempt to input data at the same time; in such situations, the user bus always has priority. A Master Enable (ME) input over the IV bus. The data latches are transparent, in that, while either bus is enabled for input, all input-data transitions are propagated to the other bus, if enabled for output. FEATURES • • • • • • Two bidirectional 8-bit busses Independent bus operation (user-bus priority for data entry) User data input synchronous with respect to MCLK 3-State TTL outputs with high-drive capabilities Power-up to predetermined logic state Directly compatible with 8X305 (or 8X300) Microcontrollers • Single +5V supply • 0.4” 24-pin DIP Page 1 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Page 2 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Page 3 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Page 4 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Page 5 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Page 6 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Page 7 of 8 www.lansdale.com Issue 0 LANSDALE Semiconductor, Inc. SL8X371 Lansdale Semiconductor reserves the right to make changes without further notice to any products herein to improve reliability, function or design. Lansdale does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. “Typical” parameters which may be provided in Lansdale data sheets and/or specifications can vary in different applications, and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by the customer’s technical experts. Lansdale Semiconductor is a registered trademark of Lansdale Semiconductor, Inc. Page 8 of 8 www.lansdale.com Issue 0