Intel NETWORK PROCESSOR IXP2800 - Manual (Page 135)

Hardware Reference Manual 135
Intel
®
IXP2800 Network Processor
Intel XScale ® Core
3.12.1.1 Data Transfers
The current rate for data transfers is four bytes, except for the Slowport. The 8-bit and 16-bit
accesses are only available in the Slowport bus. The devices connected to the Slowport dictate this
data width. The user has to configure the data width register resident in the Slowport to run a
different type of data transaction. There is no burst to Slowport.
3.12.1.2 Data Alignment
For all the CSR accesses, a 32-bit data bus is assumed. Therefore, the lower two bits of the address
bus are ignored.
For the Slowport accesses, 8-, 16-, or 32-bit data access is dictated by the external device
connected to the Slowport. The APB Bus should be able to match the data width according to
which devices it is talking to.
See Table 52 for additional details on data alignment.
Figure 30. XPI Interfaces for IXP2800 Network Processor
B1740-02
PCI
SHaC
Timer
CPP Bus
APB Bus
[31:0]
SlowPort
GPIO
UART
watchdog_reset
[3:0]
PROM
SONET/SDH
Microprocessor
Interface
Demultiplexor
Intel ® IXP2400/2800
Network Processor
XPI
[7:0]
[7:0]
rx,tx
[7:0]/[15:0]/[31:0]
Reset
Sequential
Logic
Intel
XScale ®
Core