UM10139

Philips SemiconductorsVolume 1UM10139Chapter 9: UART09.3.12 UART0 Auto-baud Control Register (U0ACR - 0xE000 C020)The UART0 Auto-baud Control Register (U0ACR) controls the process of measuring theincoming clock/data rate for the baud rate generation and can be read and written atuser’s discretion.Table 110: Auto-baud Control Register (U0ACR - 0xE000 C020) bit descriptionBit Symbol Value Description Reset value0 Start This bit is automatically cleared after auto-baud 0completion.0 Auto-baud stop (auto-baud is not running).1 Auto-baud start (auto-baud is running).Auto-baud runbit. This bit is automatically cleared after auto-baudcompletion.1 Mode Auto-baud mode select bit. 00 Mode 0.1 Mode 1.2 AutoRestart 0 No restart 01 Restart in case of time-out (counter restarts at nextUART0 Rx falling edge)7:3 - NA Reserved, user software should not write ones to 0reserved bits. The value read from a reserved bit is notdefined.8 ABEOIntClr End of auto-baud interrupt clear bit (write only 0accessible). Writing a 1 will clear the correspondinginterrupt in the U0IIR. Writing a 0 has no impact.9 ABTOIntClr Auto-baud time-out interrupt clear bit (write only 0accessible). Writing a 1 will clear the correspondinginterrupt in the U0IIR. Writing a 0 has no impact.31:10 - NA Reserved, user software should not write ones toreserved bits. The value read from a reserved bit is notdefined.09.3.13 Auto-baudThe UART0 auto-baud function can be used to measure the incoming baud-rate based onthe ”AT" protocol (Hayes command). If enabled the auto-baud feature will measure the bittime of the receive data stream and set the divisor latch registers U0DLM and U0DLLaccordingly.Auto-baud is started by setting the U0ACR Start bit. Auto-baud can be stopped byclearing the U0ACR Start bit. The Start bit will clear once auto-baud has finished andreading the bit will return the status of auto-baud (pending/finished).Two auto-baud measuring modes are available which can be selected by the U0ACRMode bit. In mode 0 the baud-rate is measured on two subsequent falling edges of theUART0 Rx pin (the falling edge of the start bit and the falling edge of the least significantbit). In mode 1 the baud-rate is measured between the falling edge and the subsequentrising edge of the UART0 Rx pin (the length of the start bit).© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 106