HPI Signal Descriptions
7-10
Table 7–4. Byte Enables for HPI Data Write Access
HBE[1:0]
HWOB = 0
First Write
HHWIL = 0
Second Write
HHWIL = 1
Effective Logical Address
LSBs (Binary)
Data Write
Type
HWOB = 1
Second Write
HHWIL = 1
First Write
HHWIL = 0
Little Endian
Big Endian
Byte
11
10
00
11
Byte
11
01
01
10
Byte
10
11
10
01
Byte
01
11
11
00
Halfword
11
00
00
10
Halfword
00
11
10
00
Word
00
00
00
00
7.2.5
Read/Write Select: HR/W
HR/W is the host read/write select input. The host must drive HR/W high to
read and low to write HPI. A host without either a read/write select output or
a read or write strobe can use an address line for this function.
7.2.6
Ready: HRDY
When active (low), HRDY indicates that the HPI is ready for a transfer to be
performed. When inactive, HRDY indicates that the HPI is busy completing the
internal portion of a current read access or a previous HPID read prefetch or
write access. HCS enables HRDY; HRDY is always low when HCS is high.
7.2.7
Strobes: HCS, HDS1, HDS2
HCS, HDS1, and HDS2 allow connection to a host that has either:
-
A single strobe output with read/write select
-
Separate read and write strobe outputs. In this case, read or write select
can be done by using different addresses.