MC68HC908GZ16 Datasheet, PDF (214/314 Pages) Motorola, Inc – Microcontrollers

Enhanced Serial Communications Interface (ESCI) Module
15.9.4 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.
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 1
214
Freescale Semiconductor