838
Chapter 23
LCD Bus Interface (LCD-I/F)
Preliminary User’s Manual U17566EE1V2UM00
23.3.4
Reading from the LCD bus
You can read from the LCD bus in word, halfword, or byte format. The following
shows typical sequences of reading words and bytes.
(1)
Reading words
Reading a word requires the transmission of four bytes.
Figure 23-6
Timing (mod80: LBTCTL0.IMD0 = 0): read word, LBWST0.WST0 = 5,
LBCYC0.CYC0 = 8, LBTCTL0.TCIS0 = 0
Note
The timing diagrams are for functional explanation purposes only without any
relevance to the real hardware implementation.
Sequence
1. A dummy read to the LBDATA0 register starts the transfer of four bytes
from the external LCD controller. The busy flag LBCTL0.BYF0 is set
immediately. The “transfer in progress” flag LBCTL0.TPF0 is set on the
rising edge of the clock.
The data that is read from LBDATA0 belongs to a previous transfer and
may be ignored.
2. When the last of the four bytes is sampled and the complete word is
available in the LBDATA0 register, the busy flag LBCTL0.BYF0 is cleared.
The LBCTL0.TPF0 flag remains set until the cycle time of the last byte has
elapsed.
3. A following read to the LBDATA0 register provides the LCD controller data
and initiates a new transfer.
Dummy read word from LBDATA0 register
Byte0
DBWR
SPCLK
DBRD
DBD[7:0]
LBCTL0.BYF0
INTLCD
LBDATA0
Word (Byte0..Byte3)
Byte1
Byte2
Byte3
Read word from LBDATA0 register
LBCTL0.TPF0
sample point
electronic components distributor