IDT88P8344 Integrated Device Technology, IDT88P8344 Datasheet - Page 46

• Manufacturer Part Number: IDT88P8344
• Description: Spi Exchange 4 X Spi-3 To Spi-4 Issue 1.0
• Manufacturer: Integrated Device Technology

Direct access registers are used for interrupts and other high-priority registers
and for access to the indirect access registers. Direct access registers can be
accessed more quickly than indirect access registers, and are used where this
access speed advantage is required. There are only a limited number of direct
access registers due to the six address lines used on the IDT88P8344. All direct
access registers are one byte wide. Most registers within the IDT88P8344 are
of the indirect access type. Indirect access registers are used for configuration,
maps, etc., that may not need to be accessed as often as the direct registers.
9.1.1 Direct register format
access registers is shown.
Bit 7 is the most significant data bit.
9.1.2 Indirect register format
are accessed from the external processor interface as successive bytes of
indirect data. The indirect register space includes 32-bit data registers and 8-
bit data registers. The directly-addressed register space includes directly-
addressable 8-bit data registers, four 8-bit data registers for indirect data access,
two 8-bit address registers for indirect data access, and an 8-bit control register
for indirect data access.
Bit 31 is the most significant data bit.
Bit 7 is the most significant data bit.
IDT88P8344 SPI EXCHANGE 4 x SPI-3 TO SPI-4
Direct Register Format
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 2 bit 0
(register 0x33)
Indirect Data (register 0x30)
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 2 bit 0
There are two distinctly different types of register access in the IDT88P8344.
All direct register accesses are one byte. The bit ordering for the direct
The internal format for 32 and 8 bit registers is shown below. The registers
Indirect Data
bit 31…bit 25
(register 0x32)
Indirect Data
bit 24…bit 16
(register 0x31)
Indirect Data
bit 15…bit 8
8
6
C[7:0]
D[7:0]
A[5:0]
Figure 34. Direct & indirect access
(register 0x30)
Indirect Data
bit 7…bit 0
46
Indirect registers are accessed through special direct access registers designed
for the purpose of allowing indirect access to the large set of registers and maps
that are needed to configure the IDT88P8344.
9.1 Register access summary
the configuration registers. The indirect registers are accessed through a
protocol where interface pins A[5:0], D[7:0], and control pins are mapped into
internal register space A[15:0], D[31:0], and Control[7:0]. The full address of
any indirectly addressed register = Module_base + Block_base + Register_offset.
The SPI Exchange device uses an indirect addressing scheme for most of
32
16
C[7:0]
D[31:0]
A[15:0]
6370 drw24
INDUSTRIAL TEMPERATURE RANGE
APRIL 10, 2006