TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual
13-45
V2.0, 2007-07
EBU, V2.0
13.7.4
Data Hold Phase (DH)
The Data Hold phase is optional. This means that it can also be programmed for a length
of zero LMBCLK clock cycles. Furthermore, it is only available for asynchronous write
accesses. The Data Hold phase extends the amount of time for which data is still held
on the bus after the rising edge of the RD/WR signal occurred. The Data Hold phase is
used to accommodate external devices that require a data hold time after the rising edge
of the RD/WR signal. The length (number of LMBCLK cycles) of the Data Hold phase is
programmed via the EBU_BUSAPx.DATAC bit field. The total number of Data Hold
phase clock cycles is calculated by multiplying the DATAC parameter (independently of
bit field EBU_BUSCONx.MULTMAP) with EBU_BUSCONx.CMULT.
The calculation of the number of LMBCLK cycles in the Data Hold phase is described in
the following table:
The equivalent control capability is available for bit field EBU_EMUBAP.DATAC, which
is multiplied by EBU_EMUBC.CMULT.
Additionally, when accessing Nand Flash Devices, a Data Hold phase can also be
extended externally by asserting the WAIT signal when the region being accessed is
programmed for external data hold delay control via bit field EBU_BUSCONx.WAIT.
Access Type
Number of Data Hold Phase Cycles
Asynchronous Write Cycle
= DATAC
×
CMULT