MC68HC05L28 Datasheet, PDF (74/156 Pages) Motorola, Inc – Flexible general-purpose microcomputer

7.1
LCD RAM
Data to be displayed on the LCD must be written into the LCD RAM. The LCD RAM is comprised
of 12 bytes of RAM (in the MC68HC05L28’s memory map) at $0040 – $004B. The 96 bits in the
LCD RAM correspond to the 96 segments that can be driven by the frontplane/backplane drivers.
Table 7-1 shows how the LCD RAM is organized. Writing a ‘1’ to a given location will result in the
corresponding display segment being activated when the DISON bit is set. The LCD RAM is a dual
port RAM that interfaces with the internal address and data buses of the MCU. It is possible to read
from LCD RAM locations for scrolling purposes. When DISON = 0, the LCD RAM can be used as
main on-chip RAM.
Table 7-1 LCD RAM organization
LCD RAM
Data
Address
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
$40
FP1-BP3 FP1-BP2 FP1-BP1 FP1-BP0 FP0-BP3 FP0-BP2 FP0-BP1 FP0-BP0
$41
FP3-BP3 FP3-BP2 FP3-BP1 FP3-BP0 FP2-BP3 FP2-BP2 FP2-BP1 FP2-BP0
7
$42
FP5-BP3 FP5-BP2 FP5-BP1 FP5-BP0 FP4-BP3 FP4-BP2 FP4-BP1 FP4-BP0
$43
FP7-BP3 FP7-BP2 FP7-BP1 FP7-BP0 FP6-BP3 FP6-BP2 FP6-BP1 FP6-BP0
$44
FP9-BP3 FP9-BP2 FP9-BP1 FP9-BP0 FP8-BP3 FP8-BP2 FP8-BP1 FP8-BP0
$45
FP11-BP3 FP11-BP2 FP11-BP1 FP11-BP0 FP10-BP3 FP10-BP2 FP10-BP1 FP10-BP0
$46
FP13-BP3 FP13-BP2 FP13-BP1 FP13-BP0 FP12-BP3 FP12-BP2 FP12-BP1 FP12-BP0
$47
FP15-BP3 FP15-BP2 FP15-BP1 FP15-BP0 FP14-BP3 FP14-BP2 FP14-BP1 FP14-BP0
$48
FP17-BP3 FP17-BP2 FP17-BP1 FP17-BP0 FP16-BP3 FP16-BP2 FP16-BP1 FP16-BP0
$49
FP19-BP3 FP19-BP2 FP19-BP1 FP19-BP0 FP18-BP3 FP18-BP2 FP18-BP1 FP18-BP0
$4A
FP21-BP3 FP21-BP2 FP21-BP1 FP21-BP0 FP20-BP3 FP20-BP2 FP20-BP1 FP20-BP0
$4B
FP23-BP3 FP23-BP2 FP23-BP1 FP23-BP0 FP22-BP3 FP122-BP2 FP22-BP1 FP22-BP0
These LCD pins are not available on the MC68HC05L28/ MC68HC705L28. The corresponding RAM bytes ($49 to $4B)
can continue to be used as main on-chip RAM.
7.2
LCD operation
The LCD driver module can operate in four modes providing different multiplex ratios and number
of backplanes as follows:
• 1/2 bias, 2 backplanes
• 1/3 bias, 2 backplanes
• 1/3 bias, 3 backplanes
• 1/4 bias, 4 backplanes
MOTOROLA
7-2
LIQUID CRYSTAL DISPLAY DRIVER MODULE
TPG
MC68HC05L28