1
A4
2
A3
3
A2
4
A1
5
A0
6
CE
7
I/O0
8
I/O1
9
I/O2
10
I/O3
11
VCC
12
VSS
13
I/O4
14
I/O5
15
I/O6
16
I/O7
17
WE
18
A17
19
A16
20
A15
21
A14
22
A13
23
A12
24
A11
25
A10
26
A9
27
A8
28
NC
29
I/O8
30
I/O9
31
I/O10
32
I/O11
33
VCC
34
VSS
35
I/O12
36
I/O13
37
I/O14
38
I/O15
39
BLE
40
BHE
41
OE
42
A7
43
A6
44
A5
U2
CY62147
1
A15
2
A14
3
A13
4
A12
5
A11
6
A10
7
A9
8
A8
9
NC
10
NC
11
WE
12
NC
13
NC
14
NC
15
NC
16
A18
17
A17
18
A7
19
A6
20
A5
21
A4
22
A3
23
A2
24
A1
25
A0
26
CE
27
VSS
28
OE
29
DQ0
30
DQ8
31
DQ1
32
DQ9
33
DQ2
34
DQ10
35
DQ3
36
DQ11
37
VDD
38
DQ4
39
DQ12
40
DQ5
41
DQ13
42
DQ6
43
DQ14
44
DQ7
45
DQ15
46
VSS
47
NC
48
A16
U3
SST39VF800A
1
1OE
2
1Q1
3
1Q2
4
GND
5
1Q3
6
1Q4
7
VCC
8
1Q5
9
1Q6
10
GND
11
1Q7
12
1Q8
13
2Q1
14
2Q2
15
GND
16
2Q3
17
2Q4
18
VCC
19
2Q5
20
2Q6
21
GND
22
2Q7
23
2Q8
24
2OE
25
2LE
26
2D8
27
2D7
28
GND
29
2D6
30
2D5
31
VCC
32
2D4
33
2D3
34
GND
35
2D2
36
2D1
37
1D8
38
1D7
39
GND
40
1D6
41
1D5
42
VCC
43
1D4
44
1D3
45
GND
46
1D2
47
1D1
48
1LE
U1
74X16373
EPI0
EPI1
EPI2
EPI3
EPI4
EPI5
EPI6
EPI7
EPI8
EPI9
EPI10
EPI11
EPI12
EPI13
EPI14
EPI15
EPI30
+3.3V
GND
GND
A[0:15]
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
A15
A[0:15]
EPI_16_BUS
EPI_16_BUS
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
A15
EPI16
EPI17
EPI0
EPI1
EPI2
EPI3
EPI4
EPI5
EPI6
EPI7
EPI8
EPI9
EPI10
EPI11
EPI12
EPI13
EPI14
EPI15
EPI28
EPI29
EPI26
EPI25
EPI24
A[0:15]
EPI_16_BUS
EPI_16_BUS
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
A15
EPI16
EPI17
EPI18
EPI0
EPI1
EPI2
EPI3
EPI4
EPI5
EPI6
EPI7
EPI8
EPI9
EPI10
EPI11
EPI12
EPI13
EPI14
EPI15
EPI29
EPI28
EPI27
EPI_16_BUS
GND
+3.3V
+3.3V
GND
Host Bus Mode
1247
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
External Peripheral Interface (EPI)
Figure 17-7. Example Schematic for Muxed Host-Bus 16 Mode
17.7.2 Speed of Transactions
The COUNT0 field in the EPIBAUD register must be configured to set the main transaction rate based on
what the slave device can support (including wiring considerations). The main control transitions are
normally ½ the baud rate (COUNT0 = 1) because the EPI block forces data vs. control to change on
alternating clocks. When using dual chip selects, each chip select can access the bus using differing baud
rates by setting the CSBAUD bit in the EPIHBnCFG2 register. In this case, the COUNT0 field controls the
CS0 transactions, and the COUNT1 field controls the CS1 transactions. When using quad chip select
mode, the COUNT0 bit field of the EPIBAUD2 register controls the baud rate of CS2 and the COUNT1 bit
field is programmed to control the baud rate of CS3.