Register Descriptions
1236
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
External Peripheral Interface (EPI)
Table 17-19. EPI Host-Bus 16 Configuration (EPIHB16CFG) Register Field Descriptions (continued)
Bit
Field
Value
Description
30
CLKGATEI
Clock Gated when Idle
0
The EPI clock is free running
Note that EPI0S32 is an iRDY signal if RDYEN is set. CLKGATEI is ignored if CLKPIN is 0 or if the
COUNT0 field in the EPIBAUD register is cleared.
1
The EPI clock is output only when there is data to write or read (current transaction); otherwise the
EPI clock is held low
29
CLKINV
Invert Output Clock Enable
0
No effect
1
Invert EPI clock to ensure the rising edge is centered for outbound signal's setup and hold. Inbound
signal is captured on rising edge EPI clock.
28
RDYEN
Input Ready Enable
0
No effect
1
An external ready can be used to control the continuation of the current access. If this bit is set and
the iRDY signal (EPIS032) is low, the current access is stalled.
27
IRDYINV
Input Ready Invert
0
No effect
1
Invert the polarity of incoming external ready (iRDY signal). If this bit is set and the iRDY signal
(EPIS032) is high the current access is stalled.
26-24
Reserved
Reserved
23
XFFEN
External FIFO FULL Enable
0
No effect.
1
An external FIFO full signal can be used to control write cycles. If this bit is set and the FFULL full
signal is high, XFIFO writes are stalled.
22
XFEEN
External FIFO EMPTY Enable
0
No effect
1
An external FIFO empty signal can be used to control read cycles. If this bit is set and the FEMPTY
signal is high, XFIFO reads are stalled.
21
WRHIGH
WRITE Strobe Polarity
0
The WRITE strobe for CS0 is WR (active Low).
1
The WRITE strobe for CS0 is WR (active High).
20
RDHIGH
READ Strobe Polarity
0
The READ strobe for CS0 is RD (active Low).
1
The READ strobe for CS0 is RD (active High).
19
ALEHIGH
ALE Strobe Polarity
0
The address latch strobe for CS0 accesses is ALE (active Low).
1
The address latch strobe for CS0 accesses is ALE (active High).
18-17
Reserved
Reserved
16
BURST
Burst Mode
Burst mode must be used with an ALE-enabled interface. Burst mode must be used with ADMUX,
which is configured by the MODE field in the EPIHB16CFG register.
Note: Burst mode is optimized for word-length accesses.
0
Burst mode is disabled.
1
Burst mode is enabled for CS0 or single chip access.
15-8
MAXWAIT
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.
Note:
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.