SystemClockFreq
EPIClockFreq
COUNTn
1
2
2
§
·
ª
º
u
¨
¸
«
»
¬
¼
©
¹
EPIClockFreq
SystemClockFreq
EPI Registers
1126
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
External Peripheral Interface (EPI)
16.5.3 EPIBAUD2 Register (Offset = 0x8) [reset = 0x0]
EPI Main Baud Rate (EPIBAUD2)
The system clock is used internally to the EPI Controller. The baud rate counter can be used to divide the
system clock down to control the speed on the external interface. If the mode selected emits an external
EPI clock, this register defines the EPI clock emitted. If the mode selected does not use an EPI clock, this
register controls the speed of changes on the external interface. Care must be taken to program this
register properly so that the speed of the external bus corresponds to the speed of the external peripheral
and puts acceptable current load on the pins. COUNT0 and COUNT1 are used in quad chip select mode
when different baud rates are selected,
. If different baud rates are used,
COUNT0 is associated with the address range specified by CS2n and COUNT1 is associated with the
address range specified by CS3n.
The COUNTn field is not a straight divider or count. The EPI Clock on EPI0S31 is related to the COUNTn
field and the system clock as follows:
If COUNTn = 0,
(59)
otherwise:
(60)
where the symbol around COUNTn /2 is the floor operator, meaning the largest integer less than or equal
to COUNTn /2.
So, for example, a COUNTn of 0x0001 results in a clock rate of 1/2(system clock); a COUNTn of 0x0002
or 0x0003 results in a clock rate of 1/4 (system clock).
EPIBAUD2 is shown in
and described in
.
Return to
Figure 16-32. EPIBAUD2 Register
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
COUNT1
COUNT0
R/W-0x0
R/W-0x0
Table 16-16. EPIBAUD2 Register Field Descriptions
Bit
Field
Type
Reset
Description
31-16
COUNT1
R/W
0x0
CS3n Baud Rate Counter 1 This bit field contains a counter used to
divide the system clock by the count.
A count of 0 means the system clock is unchanged.
This bit field is only valid when quad chip selects are enabled by
setting the CSCFGEXT bit to 1 and the CSCFG field to 0x1 or 0x2.
In addition, the CSBAUD bit must be set in the EPIHBnCFG2
register.
15-0
COUNT0
R/W
0x0
CS2n Baud Rate Counter 0 This bit field contains a counter used to
divide the system clock by the count.
A count of 0 means the system clock is unchanged.
This bit field is only valid when quad chip selects are enabled by
setting the CSCFGEXT to 1 and the CSCFG field to 0x1 or 0x2.
In addition, the CSBAUD bit must be set in the EPIHBnCFG2
register.