XL Bus Arbiter
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 10-11

10.3.3.3 Arbiter Status Register (XARB_SR)

The arbiter status register indicates the state of watchdog functions. When a monitored condition occurs,

the respective bit is set to 1. The bit will stay set until the bit is cleared by writing a 1 into that bit. Even if

the causal condition is removed, the bit will remain set until cleared.

10.3.3.4 Arbiter Interrupt Mask Register (XARB_IMR)

The arbiter interrupt mask register is used to enable a status bit to cause an interrupt. If the interrupt mask

and corresponding status bits are set in the arbiter status register and arbiter interrupt mask register, the

arbiter will assert the interrupt signal. Normally, an interrupt service routine would read the status register

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
R0000000000000000
W
Reset0000000000000000
1514131211109876543210
R0000000SEAMMTTATTRECWTTMBADTAT
W
Reset0000000000000000
Reg
Addr
MBAR + 0x0248

Figure 10-7. Arbiter Status Register (XARB_SR)

Table 10-7. XARB_SR Field Descriptions

Bits Name Description
31–9 Reserved, should be cleared.
8 SEA Slave Error Acknowledge. This bit is set when an error is detected by any slave devices during the
transfer.
7 MM Multiple Masters at priority 0. If more than 1 master is recognized at priority 0, this bit is set. Once this
occurs this bit will remain set until cleared. This bit is intended to help in tuning dynamic priority
algorithm development.
6 TTA TT Address Only. The arbiter automatically AACKs for address only TT codes. This bit is set when this
occurs.
5 TTR TT Reserved. The arbiter automatically AACKs for reserved TT codes. This bit is set when this occurs.
4 ECW External Control Word Read/Write. External Control Word Read/Write operations are not supported
on the XL bus. If either occur, the arbiter AACKs and TEAs and sets this bit.
3 TTM TBST/TSIZ mismatch. Set when an illegal/reserved TBST and TSIZ[0:2] combination occurs. These
combinations are TBST asserted and TSIZ[0:2] = 000, 001, 011, or 1xx (x is 0 or 1).
2 BA Bus Activity Tenure Time-out. Set when the bus activity time-out counter expires.
1 DT Data Tenure Time-out. Set when the data tenure time-out counter expires.
0 AT Address Tenure Time-out. Set when the address tenure time-out counter expires.