Typewriter User Manual

MOTOROLA MC68340 USER’S MANUAL 3- 23
3.4.2 LPSTOP Broadcast Cycle
The low power stop (LPSTOP) broadcast cycle is generated by the CPU32 executing the
LPSTOP instruction. Since the external bus interface must get a copy of the interrupt
mask level from the CPU32, the CPU32 performs a CPU space type 3 write with the mask
level encoded on the data bus, as shown in the following figure. The CPU space type 3
cycle waits for the bus to be available, and is shown externally to indicate to external
devices that the MC68340 is going into LPSTOP mode. If an external device requires
additional time to prepare for entry into LPSTOP mode, entry can be delayed by asserting
HALT. The SIM40 provides internal DSACK≈ response to this cycle. For more information
on how the SIM40 responds to LPSTOP mode, see Section 4 System Integration
Module.
1514131211109876543210
—————————————I2I1 I0
I2–I0—Interrupt Mask Level
The interrupt mask level is encoded on bits 2–0 of the data bus during an LPSTOP
broadcast.
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