Filter
Top Products
Rev. 1.00, 05/04, page 397 of 544
15.4.2 LPC I/O Cycles
There are ten kinds of LPC transfer cycle: memory read, memory write, I/O read, I/O write, DMA
read, DMA write, bus master memory read, bus master memory write, bus master I/O read, and
bus master I/O write. Of these, the chip's LPC supports only I/O read and I/O write cycles.
An LPC transfer cycle is started when the LFRAME signal goes low in the bus idle state. If the
LFRAME signal goes low when the bus is not idle, this means that a forced termination (abort) of
the LPC transfer cycle has been requested.
In an I/O read cycle or I/O write cycle, transfer is carried out using LAD3 to LAD0 in the
following order, in synchronization with LCLK. The host can be made to wait by sending back a
value other than B′0000 in the slave's synchronization return cycle, but with the chip's LPC a
value of B′0000 is always returned.
If the received address matches the host address in an LPC register (IDR, ODR, STR, TWR), the
host interface enters the busy state; it returns to the idle state by output of a state count 12
turnaround. Register and flag changes are made at this timing, so in the event of a transfer cycle
forced termination (abort) before state #12, registers and flags are not changed.
I/O Read Cycle I/O Write Cycle
State
Count Contents
Drive
Source
Value
(3 to 0) Contents
Drive
Source
Value
(3 to 0)
1 Start Host 0000 Start Host 0000
2 Cycle type/direction Host 0000 Cycle type/direction Host 0010
3 Address 1 Host Bits 15 to
12
Address 1 Host Bits 15 to
12
4 Address 2 Host Bits 11 to 8 Address 2 Host Bits 11 to 8
5 Address 3 Host Bits 7 to 4 Address 3 Host Bits 7 to 4
6 Address 4 Host Bits 3 to 0 Address 4 Host Bits 3 to 0
7 Turnaround
(recovery)
Host 1111 Data 1 Host Bits 3 to 0
8 Turnaround None ZZZZ Data 2 Host Bits 7 to 4
9 Synchronization Slave 0000 Turnaround
(recovery)
Host 1111
10 Data 1 Slave Bits 3 to 0 Turnaround None ZZZZ
11 Data 2 Slave Bits 7 to 4 Synchronization Slave 0000
12 Turnaround
(recovery)
Slave 1111 Turnaround
(recovery)
Slave 1111
13 Turnaround None ZZZZ Turnaround None ZZZZ