SN32F280 Series
32-Bit Cortex-M0 Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 216
Version 1.1
- Write timing waveform in the A
N
D16ALE mode:
AD[15:0]
ADDR[16:1]
ADDRSETUP
(1, 2, 3, …)
WESETUP
(0, 1, 2, …)
WRSTRB
(1, 2, 3, …)
A[N-1:16]
CSn
OE
DATA[15:0]
WEHOLD
(0, 1, 2, …)
ADDR[N:17]
ALE
ADDRHOLD
(0, 1, 2, …)
18.5.4 Write Buffer and EBI Status
The EBI has a 32-bit wide write buffer. The write buffer can be used to limit stalling of an AHB write burst transaction
which comes from the Cortex-M0 to a potentially slow external device.
The EBIBUSY status bit in the
register indicates whether an AHB transaction is still active in the EBI or
not. When performing an AHB read or write, the EBIBUSY bit stays 1 until the required transaction(s) with the external
device has finished.
18.5.5 Bus Turn-around and Idle Cycles
The EBI_AD lines can be driven by either the EBI or the external device depending on the cycle state of EBI bus. The
RDHOLD timing parameter is for the bus turn-around time and should be programmed to ensure enough time for the
characteristics of an external device.
The default setting for the EBI is to insert an IDLE cycle between EBI transactions to the same bank. The IDLE cycle
insertion is shown for two back-to-back read transactions in Figure 185. For cases where the IDLE state can also
provide the required bus turn-around time, the RDHOLD parameter can be programmed to 0. For increased EBI access
performance, the automatic IDLE state insertion can be disabled by setting the NOIDLEn bits in the EBICR register to 1.
This example is shown in Figure 186 for two back-to-back reads in a non-multiplexed address mode.
An IDLE cycle will automatically be inserted for the following cases:
Between two external device transactions to the same bank when the NOIDLEn bit is 0.
Between two external device transactions to different banks.
Between a read and a subsequent write on the EBI_AD lines.
When no request for an external transaction is available in the EBI.
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