MC68HC16Z1CAG16 Datasheet, PDF (144/500 Pages) Freescale Semiconductor, Inc – M68HC16Z Series users manual

Freescale Semiconductor, Inc.
MCU
ADDRESS DEVICE (S0)
1) SET R/W TO READ
2) DRIVE ADDRESS ON ADDR[23:0]
3) DRIVE FUNCTION CODE ON FC[2:0]
4) DRIVE SIZ[1:0] FOR OPERAND SIZE
ASSERT AS AND DS (S1)
DECODE DSACK (S3)
LATCH DATA (S4)
PERIPHERAL
PRESENT DATA (S2)
1) DECODE ADDR, R/W, SIZ[1:0], DS
2) PLACE DATA ON DATA[15:0] OR
DATA[15:8] IF 8-BIT DATA
3) DRIVE DSACK SIGNALS
NEGATE AS AND DS (S5)
START NEXT CYCLE (S0)
TERMINATE CYCLE (S5)
1) REMOVE DATA FROM DATA BUS
2) NEGATE DSACK
Figure 5-12 Word Read Cycle Flowchart
RD CYC FLOW
5.6.2.2 Write Cycle
During a write cycle, the MCU transfers data to an external memory or peripheral de-
vice. If the instruction specifies a long-word or word operation, the MCU attempts to
write two bytes at once. For a byte operation, the MCU writes one byte. The portion of
the data bus upon which each byte is written depends on operand size, peripheral ad-
dress, and peripheral port size.
Refer to 5.5.2 Dynamic Bus Sizing and 5.5.4 Misaligned Operands for more infor-
mation. Figure 5-13 is a flowchart of a write-cycle operation for a word transfer. Refer
to the SIM Reference Manual (SIMRM/AD) for more information.
5-38
SYSTEM INTEGRATION MODULE
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M68HC16 Z SERIES
USER’S MANUAL