HPI Signal Descriptions
7-7
Host-Port Interface
7.2
HPI Signal Descriptions
The external HPI interface signals implement a flexible interface to a variety
of host devices. Table 7–1 lists the HPI pins and their functions. The remainder
of this section discusses the pins in detail.
Table 7–1. HPI External Interface Signals
Signal
Name
Signal Type
{
Signal
Count
Host Connection
Signal Function
HD[15:0]
I/O/Z
16
Data bus
HCNTL[1:0]
I
2
Address or control lines
HPI access type control
HHWIL
I
1
Address or control lines
Halfword identification input
HAS
I
1
Address latch enable (ALE),
address strobe, or unused
(tied high)
Differentiation between address
2nd data values on multiplexed ad-
dress/data host
HBE[1:0]
I
2
Byte enables
Data write byte enables
HR/W
I
1
Read/write strobe, address
line, or multiplexed address/
data
Read/write select
HCS
I
1
Address or control lines
Data strobe inputs
HDS[1:2]
I
1
1
Read strobe and write
strobe or data strobe
Data strobe inputs
HRDY
O
1
Asynchronous ready
Ready status of current HPI access
HINT
O
1
Host interrupt input
Interrupt signal to host
{
I = input, O = output, Z = high impedance
7.2.1
Data Bus: HD[15:0]
HD[15:0] is a parallel, bidirectional, 3-state data bus. HD is placed in the high-
impedance state when it is not performing an HPI read access.
7.2.2
Access Control Select: HCNTL[1:0]
HCNTL[1:0] indicate which internal HPI register is being accessed. The states
of these two pins select access to the HPI address (HPIA), HPI data (HPID), or
HPI control (HPIC) registers. Additionally, the HPID register can be accessed
with an optional automatic address increment. Table 7–2 describes the
HCNTL[1:0] bit functions.