837
LCD Bus Interface (LCD-I/F)
Chapter 23
Preliminary User’s Manual U17566EE1V2UM00
(3)
Writing bytes
Writing consecutive bytes transmits these bytes to the external LCD controller/
driver.
Figure 23-5
Timing (mod68 mode: LBTCTL0.IMD0 = 1): write consecutive bytes,
LBWST0.WST0 = 5, LBCYC0.CYC0 = 8, , LBCTL0.TCIS0 = 0
Note
The timing diagrams are for functional explanation purposes only without any
relevance to the real hardware implementation.
Sequence
1. The first byte of LCD data is written to the LBDATA0 register. The internal
bus transfer takes some clocks until the register of the interface 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 is started. The flag
LBCTL0.TPF0 is set to indicate that a transfer is in progress.
3. Caused by the interrupt, the DMA writes a second byte to LBDATA0. The
CPU can write this byte 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. Since the transfer (one byte) on the external bus interface is still going on
and the LBDATA0 register contents can not be copied to the write buffer
immediately, the busy flag LBCTL0.BYF0 remains set.
5. After the transfer on 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 1st byte to LBDATA0 register
SPCLK
DBWR(R/W)
DBD[7:0]
LBDATA0
internal
write buffer
DBRD(E)
LBCTL.EL=0
LBCTL0.TPF0
LBCTL0.BYF0
INTLCD
DBRD(E)
LBCTL.EL=1
1st byte
3rd byte
2nd byte
1st byte
2nd byte
3rd byte
1st byte
2nd byte
3rd byte
write 2nd byte to LBDATA0 register
write 3rd byte to LBDATA0 register
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