UHPI_HDS1
UHPI_HDS2
UHPI_HCS
UHPI_HRDY
Internal
HSTRB
Internal
HRDY
Architecture
963
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Host Port Interface (HPI)
21.2.6.4
UHPI_HDS2, UHPI_HDS1, and UHPI_HCS: Data Strobing and Chip Selection
As shown in
, the strobing logic is a function of three key inputs: the chip select pin
(UHPI_HCS) and two data strobe signals (UHPI_HDS1 and UHPI_HDS2). The internal strobe signal,
which is referred to as internal HSTRB throughout this document, functions as the actual strobe signal
inside the HPI. UHPI_HCS must be low (HPI selected) during strobe activity on the UHPI_HDS pins. If
UHPI_HCS remains high (HPI not selected), activity on the UHPI_HDS pins is ignored.
Figure 21-3. HPI Strobe and Select Logic
Strobe connections between the host and the HPI depend in part on the number and types of strobe pins
available on the host.
describes some options for connecting to the UHPI_HDS pins.
Notice in
that UHPI_HRDY is also gated by UHPI_HCS. If UHPI_HCS goes high (HPI not
selected), UHPI_HRDY goes low, regardless of whether the current internal transfer is completed in the
processor.
NOTE:
The UHPI_HCS input and one UHPI_HDS strobe input can be tied together and driven with
a single strobe signal from the host. This technique selects the HPI and provides the strobe,
simultaneously. When using this method, be aware that UHPI_HRDY is gated by UHPI_HCS
as previously described.
It is not recommended to tie both UHPI_HDS1 and UHPI_HDS2 to static logic levels and use
UHPI_HCS as a strobe.
(1)
The UHPI_HR/W signal could be driven by a host address line in this case.
Table 21-3. Options for Connecting Host and HPI Data Strobe Pins
Available Host Data Strobe Pins
Connections to HPI Data Strobe Pins
Host has separate read and write strobe
pins, both active-low
Connect one strobe pin to UHPI_HDS1 and the other to UHPI_HDS2
(1)
. Since such a
host might not provide a R/W line, take care to satisfy UHPI_HR/W timings as stated in
your device-specific data manual. This could possibly be done using a host address
line.
Host has separate read and write strobe
pins, both active-high
Connect one strobe pin to UHPI_HDS1 and the other to UHPI_HDS2
(1)
. Since such a
host might not provide a R/W line, take care to satisfy UHPI_HR/W timings as stated in
your device-specific data manual. This could possibly be done using a host address
line.
Host has one active-low strobe pin
Connect the strobe pin to UHPI_HDS1 or UHPI_HDS2, and connect the other pin to
logic-level 1.
Host has one active-high strobe pin
Connect the strobe pin to UHPI_HDS1 or UHPI_HDS2, and connect the other strobe
pin to logic-level 0.