EPI Registers
1131
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
External Peripheral Interface (EPI)
Table 16-18. EPIHB8CFG Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
15-8
MAXWAIT
R/W
0xFF
Maximum Wait
This field defines the maximum number of external clocks to wait
while an external FIFO ready signal is holding off a transaction
(FFULL and FEMPTY).
When the MAXWAIT value is reached the ERRRIS interrupt status
bit is set in the EPIRIS register.
When this field is clear, the transaction can be held off forever
without a system interrupt.
When the MODE field is configured to be 0x2 and the BLKEN bit is
set in the EPICFG register, enabling HB8 mode, this field defaults to
0xFF.
7-6
WRWS
R/W
0x0
Write Wait States
This field adds wait states to the data phase of CS0n (the address
phase is not affected).
The effect is to delay the rising edge of WRn (or the falling edge of
WR).
Each wait state adds 2 EPI clock cycles to the access time.
The WRWSM bit in the EPIHB8TIME register can decrease the
number of wait states by 1 EPI clock cycle for greater granularity.
This field is not applicable in BURST mode.
This field is used in conjunction with the EPIBAUD register.
0x0 = Active WRn is 2 EPI clocks.
0x1 = Active WRn is 4 EPI clocks.
0x2 = Active WRn is 6 EPI clocks.
0x3 = Active WRn is 8 EPI clocks.
5-4
RDWS
R/W
0x0
Read Wait States
This field adds wait states to the data phase of CS0n (the address
phase is not affected).
The effect is to delay the rising edge of RDn/Oen (or the falling edge
of RD).
Each wait state adds 2 EPI clock cycles to the access time.
The RDWSM bit in the EPIHB8TIME register can decrease the
number of wait states by 1 EPI clock cycle for greater granularity.
This field is not applicable in BURST mode.
This field is used in conjunction with the EPIBAUD register
0x0 = Active RDn is 2 EPI clocks.
0x1 = Active RDn is 4 EPI clocks.
0x2 = Active RDn is 6 EPI clocks.
0x3 = Active RDn is 8 EPI clocks.
3-2
RESERVED
R
0x0
1-0
MODE
R/W
0x0
Host Bus Sub-Mode
This field determines which of four Host Bus 8 sub-modes to use.
Sub-mode use is determined by the connected external peripheral.
See for information on how this bit field affects the operation of the
EPI signals.
When used with multiple chip select option and the CSBAUD bit is
set to 1 in the EPIHB8CFG2 register, this configuration is for CS0n.
If the multiple chip select option is enabled and CSBAUD is clear, all
chip-selects use the MODE encoding programmed in this register.
0x0 = ADMUX - AD[7:0]. Data and Address are muxed.
0x1 = ADNONMUX - D[7:0]. Data and address are separate.
0x2 = Continuous Read - D[7:0]. This mode is the same as
ADNONMUX, but uses address switch for multiple reads instead of
OEn strobing.
0x3 = XFIFO - D[7:0]. This mode adds XFIFO controls with sense of
XFIFO full and XFIFO empty. This mode uses no address or ALE.
The XFIFO can only be used in asynchronous mode.