Preliminary W928C73
Publication Release Date: June 2000
- 21 - Revision A1
The auto-reload condition:
1. When 8 bits down counter overflow (From "01H" change to "FFH")
2. ENBUZ or ENBT signal rising edge (From "L" change to "H")
The divider reset condition:
1. RESET
2. MOV TONE,#I instruction
3. ENBUZ rising edge
RTC Timer and LCD Frequency
The W928C73 provides flexible RTC timer for real time clock calculation. The 8 bit auto-reload down-
counter, RTLCD, can download a suitable value for different main clock frequency to generate the
clock interrupt. For 76800Hz crystal, the RTLCD value should be 74. This RTC timer is also used to
provide the LCD frequency source.
LCD Controller/Driver
The W928C73 can directly drive a LCD with 32 segment output pins and 4 common output pins for a
total of 36
×
4 dots. LCDR is used for the LCD driver control. The alternating frequency of the LCD can
be set as 64 Hz, 128 Hz, 256 Hz, or 512 Hz. In addition, LCDON (LCDR.0) bit can also be used to set
up four of the LCD driver output pins (segment 0 to segment 31/35) as a I/O port. (For 76.8 KHz and
RTLCD = 74).
The LCD driving potentials are connected to external through port 2.4~2.6 while LCDON is set to 1.
The pin connections and output waveforms for the 1/3 bias, 1/4 duty LCD driving modes are shown
below.
P2.6
P2.5
P2.4
LCD_ON
1
0
1
0
1
0
Vcc
Vlcd3
Vlcd2
Vlcd1
VDD2
VDD1
VSS
VDD3
VDD2
VDD1
VSS
VDD3
LCD driver
outputs for
seg. on COM1
COM2 sides
being lit
LCD driver
outputs for
seg. on COM0
COM2,3 sides
being lit
VDD2
VDD1
VSS
VDD3
LCD driver
outputs for
seg. on COM0
COM1,2,3 sides
being lit
LCD Voltage Pin Connection and Output Waveform (1/3 Bias 1/4 Duty)