s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 149

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

13.9 ESCI Arbiter
The ESCI module comprises an arbiter module designed to support software for communication tasks as
bus arbitration, baud rate recovery and break time detection. The arbiter module consists of an 9-bit
counter with 1-bit overflow and control logic. The can control operation mode via the ESCI arbiter control
register (SCIACTL).
13.9.1 ESCI Arbiter Control Register
AM1 and AM0 — Arbiter Mode Select Bits
ALOST — Arbitration Lost Flag
ACLK — Arbiter Counter Clock Select Bit
AFIN— Arbiter Bit Time Measurement Finish Flag
ARUN— Arbiter Counter Running Flag
Freescale Semiconductor
These read/write bits select the mode of the arbiter module as shown in
This read-only bit indicates loss of arbitration. Clear ALOST by writing a 0 to AM1.
This read/write bit selects the arbiter counter clock source.
This read-only bit indicates bit time measurement has finished. Clear AFIN by writing any value to
SCIACTL.
This read-only bit indicates the arbiter counter is running.
1 = Arbiter counter is clocked with one half of the ESCI input clock generated by the ESCI prescaler
0 = Arbiter counter is clocked with the bus clock divided by four
1 = Bit time measurement has finished
0 = Bit time measurement not yet finished
1 = Arbiter counter running
0 = Arbiter counter stopped
Reset:
Read:
Write:
For ACLK = 1, the arbiter input clock is driven from the ESCI prescaler. The
prescaler can be clocked by either the bus clock or BUSCLKX4 depending
on the state of the ESCIBDSRC bit in configuration register.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
Bit 7
AM1
Figure 13-18. ESCI Arbiter Control Register (SCIACTL)
0
AM[1:0]
Table 13-11. ESCI Arbiter Selectable Modes
= Unimplemented
0 0
0 1
1 0
1 1
ALOST
6
0
AM0
5
0
Idle / counter reset
Bit time measurement
Bus arbitration
Reserved / do not use
ACLK
NOTE
4
0
ESCI Arbiter Mode
AFIN
3
0
ARUN
2
0
AROVFL
Table
1
0
13-11.
ARD8
Bit 0
0
ESCI Arbiter
149