676Chapter 16 Clocked Serial Interface B (CSIB)User’s Manual U16580EE3V1UD0016.7.3 Baud rate generationThe transmission/reception clock is generated by dividing the main clock. The baud rate generated fromthe main clock is obtained by the following equation.Remarks: 1. f BRGm: BRGm count clock2. fBGCSm: Clock frequency selected by the BGCSm1, BGCSm0 bits of the PRSMmregister.3. fXX: Main clock oscillation frequency4. k: PRSMm register setting value (2 ≤ k ≤ 5)5. N: PRSCMm register setting value (1 to 255), when PRSCMm = 01H to FFH,or N = 256, when PRSCMm = 00H.6. m = 0, 116.8 CautionsIn communication modes where CBnCTL1.CBnDAP bit = 1, the CBnSTR.CBnTSF bit is cleared half aSCKBn clock after occurrence of a reception completion interrupt (INTCBnR).In the single transfer mode, writing the next transmit data is ignored during communication(CBnTSF bit = 1), and the next transfer is not started. Also if reception-only communication(CBnCTL0.CBnTXE bit = 0, CBnCTL0.CBnRXE bit = 1) is set, the next transfer is not started even if thereceive data is read during communication (CBnTSF bit = 1).Therefore, when using the single transfer mode with communication modes where CBnCTL1.CBnDAPbit = 1, pay particular attention to the following:• To start the next transmission, first confirm that CBnTSF bit = 0, and then write the transmit data tothe CBnTX register.• To perform the next reception continuously in reception-only mode (CBnTXE = 0, CBnRXE = 1),confirm that CBnTSF bit = 0, and then read the CBnRX register.If communication is supported by DMA transfer function, only communication modes with CBnDAPbit = 0 should be used.f BRGmf BGCSmN 2×-------------------- f XX2 k N 2××--------------------------= =
