mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 553

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

24.4 Functional Description
This section provides the functional description of the module.
24.4.1 Chip-Select Operation
Each chip-select has a dedicated set of registers for configuration and control:
24.4.1.1 General Chip-Select Operation
When a bus cycle is routed to the Mini-FlexBus, the device first compares its address
with the base address and mask configurations programmed for chip-selects 0 and 1
(configured in CSCRn). The results depend on if the address matches or not as shown in
the following table.
Freescale Semiconductor, Inc.
• Chip-select address registers (CSARn) control the base address space of the chip-
• Chip-select mask registers (CSMRn) provide 16-bit address masking and access
• Chip-select control registers (CSCRn) provide port size, wait-state generation,
Reserved
select.
control.
address setup and hold times, and automatic acknowledge generation features.
Field
7–6
5–0
PS
Port size
Specifies the data port width associated with each chip-select. It determines where data is driven during
write cycles and where data is sampled during read cycles.
00
01
10
11
This read-only bitfield is reserved and always has the value zero.
Reserved
8-bit port size. Valid data sampled and driven on FB_D[7:0]
16-bit port size. Valid data sampled and driven on FB_D[15:0]. Only supported in multiplexed mode.
16-bit port size. Valid data sampled and driven on FB_AD[15:0]. Only supported in multiplexed
mode.
FB_CSCRn field descriptions (continued)
MCF51JF128 Reference Manual, Rev. 2, 03/2011
Preliminary
Description
Chapter 24 External Bus Interface (Mini-FlexBus)
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