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TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual
13-73
V2.0, 2007-07
EBU, V2.0
13.9.8
Burst Length Control
The maximum number of Burst Phases that are generated in a single access is
controlled by two parameters of register EBU_BFCON:
•
Flash burst length mode select bit FBBMSELn (n = 0, 1)
•
Fetch burst length bit field FETBLENn (n = 0, 1)
Index n refers to type 0 or type 1 Burst Flash device parameters.
With FBBMSELn = 0, the EBU generates Burst Flash access cycles with an unlimited
number of Burst Phases. This means, Burst Phases are generated in a Burst Flash
access cycle as long as data with consecutive addresses can be requested by the EBU.
Note that the length in number of LMBCLK cycles of one Burst Phase is defined by
parameter BURSTC.
With FBBMSELn = 1, the number of Burst Phases within one Burst Flash access cycle
is defined by bit field FETBLENn. In this mode, one, two, four, or eight Burst Phases can
be selected for one Burst Flash access cycle. Bit field FETBLENn determines the
maximum number of Burst Phases. If more data is requested than can be delivered by
one Burst Flash access cycle (as defined by FETBLENn), the EBU will automatically
generate the appropriate number of continuous Burst Flash access cycles to supply the
required amount of data.
13.9.9
Control of ADV and BAA Delays During Burst Flash Access
The ADV and BAA signals are delayed by half an LMBCLK clock cycle with respect to
the other control signals of the EBU. This delay can be removed via bit BFCON.EBSEn
(n = 0, 1). The default setting after reset has the delay enabled (EBSEn = 0). Index n
refers to type 0 or type 1 Burst Flash device parameters.
Note: If EBSEn = 0, it must be regarded that the ADV/BAA active/inactive time in respect
to BFCLKO can be negative. More details are defined in the AC timings of the
TC1796 Data Sheet.