Chapter 14 Serial Communication Interface (S12SCIV6)MC9S12ZVMB Family Reference Manual Rev. 1.3NXP Semiconductors 51314.5.2 Modes of Operation14.5.2.1 Run ModeNormal mode of operation.To initialize a SCI transmission, see Section 14.4.5.2, “Character Transmission”.14.5.2.2 Wait ModeSCI operation in wait mode depends on the state of the SCISWAI bit in the SCI control register 1(SCICR1).• If SCISWAI is clear, the SCI operates normally when the CPU is in wait mode.• If SCISWAI is set, SCI clock generation ceases and the SCI module enters a power-conservationstate when the CPU is in wait mode. Setting SCISWAI does not affect the state of the receiverenable bit, RE, or the transmitter enable bit, TE.If SCISWAI is set, any transmission or reception in progress stops at wait mode entry. Thetransmission or reception resumes when either an internal or external interrupt brings the CPU outof wait mode. Exiting wait mode by reset aborts any transmission or reception in progress andresets the SCI.14.5.2.3 Stop ModeThe SCI is inactive during stop mode for reduced power consumption. The STOP instruction does notaffect the SCI register states, but the SCI bus clock will be disabled. The SCI operation resumes fromwhere it left off after an external interrupt brings the CPU out of stop mode. Exiting stop mode by resetaborts any transmission or reception in progress and resets the SCI.The receive input active edge detect circuit is still active in stop mode. An active edge on the receive inputcan be used to bring the CPU out of stop mode.14.5.3 Interrupt OperationThis section describes the interrupt originated by the SCI block.The MCU must service the interruptrequests. Table 14-21 lists the eight interrupt sources of the SCI.Table 14-21. SCI Interrupt SourcesInterrupt Source Local Enable DescriptionTDRE SCISR1[7] TIE Active high level. Indicates that a byte was transferred from SCIDRH/L to thetransmit shift register.TC SCISR1[6] TCIE Active high level. Indicates that a transmit is complete.RDRF SCISR1[5] RIE Active high level. The RDRF interrupt indicates that received data is availablein the SCI data register.OR SCISR1[3] Active high level. This interrupt indicates that an overrun condition has occurred.IDLE SCISR1[4] ILIE Active high level. Indicates that receiver input has become idle.RXEDGIF SCIASR1[7] RXEDGIE Active high level. Indicates that an active edge (falling for RXPOL = 0, rising forRXPOL = 1) was detected.
