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Chapter 23
LCD Bus Interface (LCD-I/F)
Preliminary User’s Manual U17566EE1V2UM00
3. All four bytes of the word are transferred back-to-back via the external bus
interface.
4. After the transfer on the external bus interface has been completed, the
LBCTL0.TPF0 is cleared.
(2)
Writing halfwords
Writing a halfword transmits two bytes to the external LCD Controller/Driver.
Figure 23-4
Timing (mod80: LBTCTL0.IMD0 = 0): write consecutive halfwords,
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. The first halfword of LCD data is written to the LBDATA0 register. The
internal bus transfer takes some clocks until the interface register is written.
Then the busy flag LBCTL0.BYF0 is set until the data is copied to the write
buffer.
2. The LBDATA0 register contents is copied to the write buffer. This clears
LBCTL0.BYF0 and causes the interrupt output to become active for one
clock cycle. Transfer on the external bus interface starts with byte 0. The
flag LBCTL0.TPF0 is set to indicate that a transfer is in progress.
3. Caused by the interrupt, the DMA writes a second halfword to LBDATA0.
The CPU can write this halfword as well after it has checked the busy flag
LBCTL0.BYF0. The internal bus transfer again takes some clock cycles
until the LBDATA0 register is written and LBCTL0.BYF0 is set.
4. Because the transfer (two bytes) on the external bus interface is still going
on and the LBDATA0 register contents can not be copied to the write buffer
immediately, LBCTL0.BYF0 is set.
5. After the transfer over the external bus interface has been completed, the
write buffer is filled with the contents of LBDATA0. The busy flag
LBCTL0.BYF0 is cleared, and the interrupt output INTLCD becomes active
for one clock cycle.
Filling the write buffer starts a new transfer to the external LCD controller.
Write 1
st
halfword to LBDATA0 register
Byte0
Byte1
DBWR
SPCLK
DBRD
DBD[7:0]
LBCTL0.BYF0
INTLCD
LBDATA0
1
st
halfword (consists of byte0 and byte1)
Byte0
Byte1
internal
write buffer
1
st
halfword
2
nd
halfword (consists of byte0 and byte1)
2
nd
halfword
LBCTL0.TPF0
Write 2
nd
halfword to LBDATA0 register
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