The ST16C1550 and ST16C1551 UARTs (here on denoted as the ST16C155X) are improved versions of the SSI 73M1550 and SSI 73M2550 UART with higher operating speed and lower access time. The ST16C155X provides enhanced UART functions with 16 byte FIFOs, a modem control interface, independent programmable baud rate generators with clock rates up to 1.5 Mbps. Onboard status registers provide the user with error indications and operational status. System interrupt and modem control features may be tailored by external software to meet specific user requirements. An internal loopback capability allows onboard diagnostics. The baud rate generator can be configured for either crystal or external clock input with the exception of the 28 pin ST16C1551 package (where an external clock must be provided). Each package type, with the exception of the 28 pin ST16C155X, provides a buffered reset output that can be controlled through user software. DMA monitor signals TXRDY/RXRDY are not available at the ST16C155X I/O pins but these signals are accessible through ISR register bits 4-5. Except as listed above, all package versions have the same features. The ST16C155X is not compatible with the industry standard 16550 and will not work with the standard serial port driver in MS Windows (see pages 16-17 for details). For an MS Windows compatible UART, see the ST16C550.