U-Bus to IMB3 Bus Interface (UIMB)
MPC561/MPC563 Reference Manual, Rev. 1.2
12-4
Freescale Semiconductor
It is possible for multiple interrupt sources to assert the same interrupt level. To reduce the latency, it is a
good practice for each interrupt source to assert an interrupt on a level on which no other interrupt source
is mapped.
12.4.2
IMB3 Interrupt Multiplexing
The IMB3 has 10 lines for interrupt support. Eight lines are for interrupts and two are for interrupt level
byte select (ILBS). These lines will transfer the 32 interrupt levels to the interrupt synchronizer. A diagram
of the interrupt flow is shown in
Figure 12-4. Interrupt Synchronizer Signal Flow
Latching 32 interrupt levels using eight IMB3 interrupt lines is accomplished with a 4:1 time-multiplexing
scheme. The UIMB drives two signals (ILBS[0:1]) with a multiplexer select code that tells all interrupting
modules on the IMB3 about which group of signals to drive during the next clock. See
12.4.3
ILBS Sequencing
The IMB3 interface drives the ILBS signals continuously, incrementing through a code sequence (0b00,
0b01, 0b10, 0b11) once every clock. The UMCR[IRQMUX] bits in the IMB3 module configuration
register select which type of multiplexing the interrupt synchronizer will perform. The IRQMUX field can
select time-multiplexing protocols for 8, 16, 24 or 32 interrupt sources. These protocols would take one,
two, three or four clocks, respectively.
shows ILBS sequencing. Programming IRQMUX[0:1] to 0b00 disables time multiplexing. In
this case the ILBS lines remain at 0b00 at all times. In this mode, no interrupts from IMB3 modules which
assert on levels 8 through 31 are ever latched by the interrupt synchronizer. SRESET will not clear the
IRQMUX bits, so time multiplexing will be enabled with the previous setup after SRESET is released.
The timing for the scheme and the values of ILBS and the interrupt levels driven onto the IMB3 IRQ lines
are shown in
. This scheme causes a maximum latency of four clocks and an average latency
of two clocks before the interrupt request can reach the interrupt synchronizer.
UIPEND
IMB3 Interrupt
8
Block
Byte Count
Byte-enables
[24:31]
[16:23]
[8:15]
[0:7]
8
to IMB3
Byte-enable
2
4
U-bus Interrupt
U-bus
Level[0:7]
Register
Data[0:31]
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...