Typewriter User Manual

4- 26 MC68340 USER’S MANUAL MOTOROLA
Table 4-8. BMTx Encoding
BMT1 BMT0 Bus Monitor Timeout Period
0 0 64 system clocks (CLKOUT)
0 1 32 system clocks
1 0 16 system clocks
1 1 8 system clocks
4.3.2.6 PERIODIC INTERRUPT CONTROL REGISTER (PICR). The PICR contains the
interrupt level and the vector number for the periodic interrupt request. This register can
be read or written at any time. Bits 15–11 are unimplemented and always return zero; a
write to these bits has no effect.
PICR $022
1514131211109876543210
00000PIRQL2 PIRQL1 PIRQL0 PIV7 PIV6 PIV5 PIV4 PIV3 PIV2 PIV1 PIV0
RESET:
0000000000001111
Supervisor Only
Bits 15–11—Reserved
PIRQL2–PIRQL0—Periodic Interrupt Request Level
These bits contain the periodic interrupt request level. Table 4-9 lists which interrupt
request level is asserted during an IACK cycle when a periodic interrupt is generated.
The periodic timer continues to run when the interrupt is disabled.
Table 4-9. PIRQL Encoding
PIRQL2 PIRQL1 PIRQL0 Interrupt Request Level
0 0 0 Periodic Interrupt Disabled
0 0 1 Interrupt Request Level 1
0 1 0 Interrupt Request Level 2
0 1 1 Interrupt Request Level 3
1 0 0 Interrupt Request Level 4
1 0 1 Interrupt Request Level 5
1 1 0 Interrupt Request Level 6
1 1 1 Interrupt Request Level 7
NOTE:
Use caution with a level 7 interrupt encoding due to the
SIM40's interrupt servicing order. See 4.2.2.7 Simultaneous
Interrupts by Sources in the SIM40 for the servicing order.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc...