MC68HC908GZ8 Datasheet, PDF (253/344 Pages) Motorola, Inc – Microcontrollers

Enhanced Serial Communications Interface (ESCI) Module
ESCI Arbiter
19.9.4 Arbitration Mode
If AM[1:0] is set to 10, the arbiter module operates in arbitration mode. On every
rising edge of SCI_TxD (output of the ESCI module, internal chip signal), the
counter is started. When the counter reaches $38 (ACLK = 0) or $08 (ACLK = 1),
RxD is statically sensed. If in this case, RxD is sensed low (for example, another
bus is driving the bus dominant) ALOST is set. As long as ALOST is set, the TxD
pin is forced to 1, resulting in a seized transmission.
If SCI_TxD is sensed logic 0 without having sensed a logic 0 before on RxD, the
counter will be reset, arbitration operation will be restarted after the next rising edge
of SCI_TxD.
MC68HC908GZ8
Freescale Semiconductor
Enhanced Serial Communications Interface (ESCI) Module
Data Sheet
253