HT1620 RAM Mapping 32´4 LCD Controller for I/O mC Features · · · · · · · · · Logic operating voltage: 2.4V~3.3V LCD voltage: 3.6V~4.9V Low operating current <3mA at 3V External 32.768kHz crystal oscillator Selection of 1/2 or 1/3 bias, and selection of 1/2 or 1/3 or 1/4 duty LCD applications Internal time base frequency sources Two selectable buzzer frequencies (2kHz/4kHz) Built-in capacitor type bias charge pump Time base or WDT overflow output · · · · · · · · · 8 kinds of time base/WDT clock source 32´4 LCD driver Built-in 32´4-bit display RAM 3-wire serial interface Internal LCD driving frequency source Software configuration feature R/W address auto increment Data mode and command mode instructions Three data accessing modes General Description for the interface between the host controller and the HT1620. The HT1620 consumes low operating current owing to adopting capacitor type bias charge pump. The HT162X series have many kinds of products that match various applications. The HT1620 is a 128 pattern (32´4), memory mapping, and multi-function LCD driver. The S/W configuration feature of the HT1620 makes it suitable for multiple LCD applications including LCD modules and display subsystems. Only three or four lines are required Selection Table HT162X HT1620 HT1621 HT1622 HT16220 HT1623 HT1625 HT1626 HT1627 HT16270 COM 4 4 8 8 8 8 16 16 16 SEG 32 32 32 32 48 64 48 64 64 Ö Ö Ö Ö Ö Ö Ö Ö Ö Built-in Osc. Crystal Osc. Ö Ö Ö 1 Ö July 26, 1999 HT1620 Block Diagram D is p la y R A M O S C O O S C I C S R D W R C o n a n T im C ir c tro l d in g u it C O M 0 L C D D r iv e r / B ia s C ir c u it C O M 3 S E G 0 D A T A V D D S E G 3 1 V S S C C 1 C C 2 V O 1 5 N V E E B Z B Z T o n e F re q u e n c y G e n e ra to r W a tc h d o g T im e r & T im e B a s e G e n e r a to r IR Q Notes: CS: Chip selection BZ, BZ: Tone outputs WR, RD, DATA: Serial interface COM0~COM3, SEG0~SEG31: LCD outputs IRQ: Time base or WDT overflow output VO15N: Half voltage circuit output pin VEE: Double voltage circuit output pin CC1/CC2: External capacitor pin, for double voltage and half voltage circuit use 2 July 26, 1999 HT1620 Pin Assignment C S R D W R D A T A V S S O S C O O S C I V D D IR Q B Z B Z C C 1 N C 6 4 6 3 6 2 6 1 6 0 5 9 5 8 5 7 5 6 5 5 5 4 5 3 5 2 1 5 1 2 5 0 N C 3 4 9 4 N C 4 8 5 4 7 6 4 6 7 4 5 8 4 4 N C C V O 1 V C O C O C O C O S E S E S E S E S E S E S E S E S E N C C 2 5 N E E M 0 M 1 M 2 M 3 G 0 G 1 G 2 G 3 G 4 G 5 G 6 G 7 G 8 N C 9 4 3 H T 1 6 2 0 6 4 Q F P 1 0 1 1 4 2 4 1 1 2 4 0 1 3 3 9 1 4 3 8 1 5 3 7 1 6 3 6 1 7 3 5 1 8 1 9 3 4 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 N C N C N C N C S E S E S E S E S E S E S E S E S E S E S E S E N C G 3 1 G 3 0 G 2 9 G 2 8 G 2 7 G 2 6 G 2 5 G 2 4 G 2 3 G 2 2 G 2 1 G 2 0 N C S E S E S E S E S E S E S E S E S E S E S E N C G 1 9 G 1 8 G 1 7 G 1 6 G 1 5 G 1 4 G 1 3 G 1 2 G 1 1 G 1 0 G 9 3 July 26, 1999 HT1620 Pad Assignment C C 1 B Z B Z IR Q V D D O S C I O S C O V S S D A T A W R R D C S 5 1 5 0 4 9 4 8 4 7 4 6 4 5 4 4 4 3 4 2 4 1 4 0 1 C C 2 V O 1 5 N 2 V E E 3 C O M 0 4 C O M 1 5 6 C O M 2 C O M 3 7 S E G 0 8 S E G 1 9 S E G 2 S E G 3 3 9 S E G 3 1 3 8 S E G 3 0 1 0 3 7 S E G 2 9 1 1 3 6 S E G 2 8 S E G 4 1 2 3 5 S E G 2 7 S E G 5 1 3 3 4 S E G 2 6 3 3 S E G 2 5 3 2 S E G 2 4 (0 ,0 ) 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 S E G 6 S E G 7 S E G 8 S E G 9 S E G 1 0 S E G 1 1 S E G 1 2 S E G 1 3 S E G 1 4 S E G 1 5 S E G 1 6 S E G 1 7 S E G 1 8 S E G 1 9 Chip size: 142 ´ 141 (mil) 3 1 S E G 2 3 3 0 S E G 2 2 2 9 S E G 2 1 2 8 S E G 2 0 2 * The IC substrate should be connected to VDD in the PCB layout artwork. 4 July 26, 1999 HT1620 Pad Coordinates Unit: mil Pad No. X Y Pad No. X Y 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 -61.58 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -61.83 -60.90 -54.27 -47.64 -41.01 -34.38 -27.75 -21.12 -14.49 -7.86 -1.23 5.40 12.03 18.66 63.62 50.83 43.73 37.10 30.47 23.84 17.21 10.58 3.95 -2.68 -9.31 -15.94 -22.57 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 -64.26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 25.29 66.98 66.98 66.98 66.98 66.98 66.98 66.98 66.98 66.98 66.98 66.98 66.98 65.71 59.08 52.45 40.59 29.75 22.95 16.32 9.56 -2.21 -21.80 -39.52 -49.60 -64.26 -62.65 -56.01 -49.38 -42.76 -36.13 -29.50 -22.86 -16.24 -9.60 -2.97 3.65 10.28 64.39 64.39 64.39 64.39 64.39 64.39 64.39 64.39 64.30 64.39 64.39 63.62 5 July 26, 1999 HT1620 Pad Description Pad No. Pad Name I/O Description 2 VO15N O Half voltage circuit output pin 3 VEE ¾ Double voltage circuit output pin 4~7 COM0~COM3 O LCD common outputs 8~39 SEG0~SEG31 O LCD segment outputs I Chip selection input with pull-high resistor When the CS is logic high, the data and command, read from or written to the HT1620 are disabled. The serial interface circuit is also reset. But if the CS is at logic low level and is input to the CS pad, the data and command transmission between the host controller and the HT1620 are all enabled. 40 CS 41 RD I READ clock input with pull-high resistor Data in the RAM of the HT1620 are clocked out on the falling edge of the RD signal. The clocked out data will appear on the DATA line. The host controller can use the next raising edge to latch the clocked out data. 42 WR I WRITE clock input with pull-high resistor Data on the DATA line are latched into the HT1620 on the rising edge of the WR signal. 43 DATA I/O Serial data input/output with pull-high resistor 44 VSS ¾ Negative power supply, Ground 45 OSCO O 46 OSCI I The OSCI and OSCO pads are connected to a 32.768kHz crystal in order to generate a system clock. 47 VDD ¾ Positive power supply 48 IRQ O Time base or WDT overflow flag, NMOS open drain output 49, 50 BZ, BZ O 2kHz or 4kHz tone frequency output pair (tri-state output buffer) 51, 1 CC1, CC2 I External capacitor pin, for double voltage and half voltage circuit use Absolute Maximum Ratings o o Supply Voltage..............................-0.3V to 3.6V Storage Temperature.................-50 C to 125 C Input Voltage .................VSS-0.3V to VDD+0.3V Operating Temperature...............-25 C to 75 C o o Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maximum Ratings² may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. 6 July 26, 1999 HT1620 D.C. Characteristics Symbol Parameter Ta=25°C Test Conditions VDD Conditions ¾ Min. Typ. Max. Unit 2.4 ¾ 3.3 V VDD Operating Voltage ¾ IDD Operating Current 3V No load* ¾ 2 3 mA ISTB Standby Current 3V No load* ¾ ¾ 1 mA VIL Input Low Voltage 3V DATA, WR, CS, RD ¾ ¾ 0.6 V VIH Input High Voltage 3V DATA, WR, CS, RD 2.4 ¾ 3.0 V IOL1 DATA, BZ, BZ, IRQ 3V VOL=0.3V 0.8 1.6 ¾ mA IOH1 DATA, BZ, BZ 3V VOH=2.7V -0.6 -1.2 ¾ mA IOL2 LCD Common Sink Current 3V VOL=0.3V 80 150 ¾ mA IOH2 LCD Common Source Current 3V VOH=2.7V -70 -120 ¾ mA IOL3 LCD Segment Sink Current 3V VOL=0.3V 70 140 ¾ mA IOH3 LCD Segment Source Current 3V VOH=2.7V -30 -60 ¾ mA RPH Pull-high Resister 3V DATA, WR, CS, RD 40 80 150 kW * No load: LCD OFF, Buzzer OFF, CS=WR=RD=High A.C. Characteristics Symbol fSYS Parameter Ta=25°C Test Conditions VDD System Clock 3V LCD Frame Frequency ¾ LCD Frame Frequency 1/2 Duty ¾ LCD Frame Frequency 1/3 Duty ¾ LCD Frame Frequency 1/4 Duty ¾ tCOM LCD Common Period ¾ fCLK Serial Data Clock 3V fTONE Tone Frequency ¾ fLCD 7 Conditions Crystal 32kHz Min. Typ. Max. Unit ¾ 32 ¾ kHz ¾ 64 ¾ Hz ¾ 64 ¾ Hz ¾ 56 ¾ Hz ¾ 64 ¾ Hz n: Number of COM ¾ n/fLCD ¾ s Write mode ¾ ¾ 150 kHz Read mode ¾ ¾ 75 kHz ¾ ¾ 2 or 4 ¾ kHz Crystal 32kHz July 26, 1999 HT1620 Symbol Test Conditions Parameter tCS Serial Interface Reset Pulse Width (Figure 3) ¾ tCLK WR, RD Input Pulse Width (Figure 1) 3V tr, tf Rise/Fall Time Serial Data Clock Width (Figure 1) 3V tsu Setup Time for DATA to WR, RD Clock Width (Figure 2) th Min. Conditions VDD CS Typ. Max. Unit ¾ 250 ¾ ns Write mode 3.34 ¾ ¾ Read mode 6.67 ¾ ¾ ¾ ¾ 120 ¾ ns 3V ¾ ¾ 120 ¾ ns Hold Time for DATA to WR, RD Clock Width (Figure 2) 3V ¾ ¾ 120 ¾ ns tsu1 Setup Time for CS to WR,RD Clock Width (Figure 3) 3V ¾ ¾ 100 ¾ ns th1 Hold Time for CS to WR, RD Clock Width (Figure 3) 3V ¾ ¾ 100 ¾ ns ms V A L ID D A T A D B tf W R , R D C lo c k tr 9 0 % 5 0 % 1 0 % tC V G N D tC L K ts D D W R , R D C lo c k L K Figure 1 W R , R D C lo c k S V th u 1 5 0 % F IR S T C lo c k 5 0 % V D D G N D G N D 1 V L A S T C lo c k th u D D 5 0 % ts D D G N D Figure 2 tC C S V 5 0 % D D G N D Figure 3 8 July 26, 1999 HT1620 Functional Description Display memory - RAM structure Buzzer tone output The static display RAM is organized into 32´4 bits and stores the display data. The contents of the RAM are directly mapped to the contents of the LCD driver. Data in the RAM can be accessed by the READ, WRITE and READ-MOD IFY-WRITE commands. The following is a mapping from the RAM to the LCD patterns. A simple tone generator is implemented in the HT1620. The tone generator can output a pair of differential driving signals on the BZ and BZ which are used to generate a single tone. C O M 3 C O M 2 C O M 1 0 S E G 1 1 S E G 2 2 S E G 3 3 S E G 3 1 3 1 3 D 2 D The HT1620 is a 128 (32´4) pattern LCD driver. It can be configured as 1/2 or 1/3 bias and 2 or 3 or 4 commons of LCD driver by the S/W configuration. This feature makes the HT1620 suitable for multiple LCD applications. The LCD driving clock is derived from the system clock. The value of the driving clock is always 256Hz even when it is at a 32.768kHz crystal oscillator frequency. The LCD corresponding commands are summarized in the table. C O M 0 S E G 0 D LCD driver 1 D 0 A d d r e s s 6 b its (A 5 , A 4 , ..., A 0 ) The bold form of 1 0 0, namely 1 0 0, indicates the command mode ID. If successive commands have been issued, the command mode ID will be omitted, except for the first command. The LCD OFF command turns the LCD display off by disabling the LCD bias generator. The LCD ON command, on the other hand, turns the LCD display on by enabling the LCD bias generator. The BIAS and COM are the LCD panel related commands. With the use of the LCD related commands, the HT1620 can be compatible with most types of LCD panels. A d d r D a ta D a ta 4 b its (D 3 , D 2 , D 1 , D 0 ) RAM mapping Time base and watchdog timer - WDT The time base generator and WDT share the same divided (/256) counter. TIMER DIS/EN/CLR, WDT DIS/EN/CLR and IRQ EN/DIS are independent from each other. Once the WDT time-out occurs, the IRQ pin will stay at a logic low level until the CLR WDT or the IRQ DIS command is issued. T im e B a s e T IM E R /2 5 6 C lo c k S o u r c e V D D C L R T im e r W D T /4 Q D C K C L R IR Q E N /D IS W D T E N /D IS IR Q E N /D IS R W D T Timer and WDT configurations 9 July 26, 1999 HT1620 Name Command Code Function LCD OFF 10000000010X Turn off LCD outputs LCD ON 10000000011X Turn on LCD outputs 1000010abXcX c=0: 1/2 bias option c=1: 1/3 bias option ab=00: 2 commons option ab=01: 3 commons option ab=10: 4 commons option BIAS and COM Command format Interfacing The HT1620 can be configured by the S/W setting. There are two mode commands to configure the HT1620 resources and to transfer the LCD display data. The configuration mode of the HT1620 is called command mode, and its command mode ID is 1 0 0. The command mode consists of a system configuration command, a system frequency selection command, an LCD configuration command, a tone frequency selection command, a timer/WDT setting command, and an operating command. The data mode, on the other hand, includes READ, WRITE, and READ-MODIFY-WRITE operations. The following are the data mode IDs and the command mode ID: Only four lines are required to interface with the HT1620. The CS line is used to initialize the serial interface circuit and to terminate the communication between the host controller and the HT1620. If the CS pin is set to 1, the data and command issued between the host controller and the HT1620 are first disabled and then initialized. Before issuing a mode command or mode switching, a high level pulse is required to initialize the serial interface of the HT1620. The DATA line is the serial data input/output line. Data to be read or written or commands to be written have to be passed through the DATA line. The RD line is the READ clock input. Data in the RAM are clocked out on the falling edge of the RD signal, and the clocked out data will then appear on the DATA line. It is recommended that the host controller read in correct data during the interval between the rising edge and the next falling edge of the RD signal. The WR line is the WRITE clock input. The data, address, and command on the DATA line are all clocked into the HT1620 on the rising edge of the WR signal. There is an optional IRQ line to be used as an interface between the host controller and the HT1620. The IRQ pin can be selected as a timer output or a WDT overflow flag output by the S/W setting. The host controller can perform the time base or the WDT function by connecting with the IRQ pin of the HT1620. Operation Mode ID READ Data 110 WRITE Data 101 READ-MODIFY-WRITE Data 101 COMMAND Command 1 0 0 The mode command should be issued before the data or command is transferred. If successive commands have been issued, the command mode ID, 1 0 0, can be omitted. While the system is operating in the non-successive command or the non-successive address data mode, the CS pin should be set to ²1² and the previous operation mode will be reset also. Once the CS pin returns to ²0², a new operation mode ID should be issued first. 10 July 26, 1999 HT1620 Timing Diagrams READ mode (command code: 1 1 0) C S W R R D D A T A 1 0 1 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s 1 (M A 1 ) D 0 D 1 D 2 D 3 D a ta (M A 1 ) 1 0 1 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s 2 (M A 2 ) D 0 D 1 D 2 D 3 D a ta (M A 2 ) READ mode (successive address reading) C S W R R D 1 D A T A 1 0 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s (M A ) D 0 D 1 D 2 D 3 D a ta (M A ) D 0 D 1 D 2 D 3 D a ta (M A + 1 ) D 0 D 1 D 2 D 3 D a ta (M A + 2 ) D 0 D 1 D 2 D 3 D a ta (M A + 3 ) D 0 WRITE mode (command code: 1 0 1) C S W R D A T A 1 0 1 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s 1 (M A 1 ) D 0 D 1 D 2 D 3 D a ta (M A 1 ) 11 1 0 1 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s 2 (M A 2 ) D 0 D 1 D 2 D 3 D a ta (M A 2 ) July 26, 1999 HT1620 WRITE mode (successive address writing) C S W R 1 D A T A 1 0 A 5 A 4 A 3 A 2 A 1 A 0 D 0 D 1 D 2 D 3 D 0 D 1 D 2 D 3 D 0 D 1 D 2 D 3 D 0 D 1 D 2 D 3 D 0 M e m o ry A d d re s s (M A ) D a ta (M A ) D a ta (M A + 1 ) D a ta (M A + 2 ) D a ta (M A + 3 ) Note: It is recommended that the host controller should read with the data from the DATA line between the raising edge of the RD line and the falling edge of the next RD line. READ-MODIFY-WRITE mode (command code: 1 0 1) C S W R R D D A T A 1 1 0 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s 1 (M A 1 ) D 0 D 1 D 2 D 3 D a ta (M A 1 ) D 0 D 1 D 2 D 3 D a ta (M A 1 ) 1 0 1 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s 2 (M A 2 ) D 0 D 1 D 2 D 3 D a ta (M A 2 ) READ-MODIFY-WRITE mode (successive address accessing) C S W R R D D A T A 1 0 1 A 5 A 4 A 3 A 2 A 1 A 0 M e m o ry A d d re s s (M A ) D 0 D 1 D 2 D 3 D a ta (M A ) D 0 D 1 D 2 D 3 D a ta (M A ) 12 D 0 D 1 D 2 D 3 D a ta (M A + 1 ) D 0 D 1 D 2 D 3 D a ta (M A + 1 ) D 0 D 1 D 2 D 3 D a ta (M A + 2 ) D 0 July 26, 1999 HT1620 Command mode (command code: 1 0 0) C S W R D A T A 1 0 0 C 8 C 7 C 6 C 5 C 4 C 3 C 2 C 1 C o m m a n d 1 C 0 C 8 C o m m a n d ... C 7 C 6 C 5 C 4 C 3 C 2 C 1 C o m m a n d i C 0 C o m m a n d o r D a ta M o d e Mode (data and command mode) C S W R D A T A C o m m a n d o r D a ta M o d e A d d re s s a n d D a ta C o m m a n d o r D a ta M o d e A d d re s s a n d D a ta C o m m a n d o r D a ta M o d e A d d re s s a n d D a ta R D 13 July 26, 1999 HT1620 Application Circuits V D D 0 .1 m F C C 1 C C 2 V D D 0 .1 m F 3 M W V O 1 5 N 0 .1 m F V E E C S * O S C I R D W R D A T A m C * H T 1 6 2 0 O S C O C ry s ta l 3 2 7 6 8 H z O s c illa to r B Z R P ie z o IR Q C O M 0 ~ C O M 3 S E G 0 ~ S E G 3 1 B Z 1 /2 o r 1 /3 B ia s ; 1 /2 , 1 /3 o r 1 /4 D u ty L C D P a n e l * Notes: The connection of the IRQ and RD pin is selectable depending on the requirement of the mC. VDD=2.4V~3.3V, VEE=-1/2 VDD, VLCD (LCD voltage)=VDD-VEE=3/2 VDD=3.6V~4.9V. Adjust R (external pull-high resistance) to fit user¢s time base clock. 14 July 26, 1999 HT1620 Command Summary Name ID Command Code D/C Function Def. READ 1 1 0 A5A4A3A2A1A0D0D1D2D3 D Read data from the RAM WRITE 1 0 1 A5A4A3A2A1A0D0D1D2D3 D Write data to the RAM READ MODIFY WRITE 1 0 1 A5A4A3A2A1A0D0D D2D3 D Read and write to the RAM SYS DIS 1 0 0 0000-0000-X C Turn off both system oscillator and LCD bias generator SYS EN 1 0 0 0000-0001-X C Turn on system oscillator LCD OFF 1 0 0 0000-0001-X C Turn off LCD bias generator LCD ON 1 0 0 0000-0011-X C Turn on LCD bias generator TIMER DIS 1 0 0 0000-0100-X C Disable time base output Yes WDT DIS 1 0 0 0000-0101-X C Disable WDT time-out flag output Yes TIMER EN 1 0 0 0000-0010-X C Enable time base output WDT EN 1 0 0 0000-0111-X C Enable WDT time-out flag output TONE OFF 1 0 0 0000-1000-X C Turn off tone outputs CLR TIMER 1 0 0 0000-1101-X C Clear the contents of the time base generator CLR WDT C Clear the contents of the WDT stage C LCD 1/2 bias option ab=00: 2 commons option ab=01: 3 commons option ab=10: 4 commons option BIAS 1/2 1 0 0 0000-111X-X 1 0 0 0010-abX0-X BIAS 1/3 1 0 0 0010-abX1-X C LCD 1/3 bias option ab=00: 2 commons option ab=01: 3 commons option ab=10: 4 commons option TONE 4K 1 0 0 010X-XXXX-X C Tone frequency, 4kHz TONE 2K 1 0 0 0110-XXXX-X C Tone frequency, 2kHz IRQ DIS 1 0 0 100X-0XXX-X C Disable IRQ output IRQ EN 1 0 0 100X-1XXX-X C Enable IRQ output 15 Yes Yes Yes Yes July 26, 1999 HT1620 Name ID Command Code D/C Function Def. F1 1 0 0 101X-0000-X C Time base clock output: 1Hz The WDT time-out flag after: 4s F2 1 0 0 101X-0001-X C Time base clock output: 2Hz The WDT time-out flag after: 2s F4 1 0 0 101X-0010-X C Time base clock output: 4Hz The WDT time-out flag after: 1s F8 1 0 0 101X-0011-X C Time base clock output: 8Hz The WDT time-out flag after: 1/2 s F16 1 0 0 101X-0100-X C Time base clock output: 16Hz The WDT time-out flag after: 1/4 s F32 1 0 0 101X-0101-X C Time base clock output: 32Hz The WDT time-out flag after: 1/8 s F64 1 0 0 101X-0110-X C Time base clock output: 64Hz The WDT time-out flag after: 1/16 s F128 1 0 0 101X-0111-X C Time base clock output: 128Hz The WDT time-out flag after:1/32 s TEST 1 0 0 1110-0000-X C Test mode, user don¢t use. NORMAL 1 0 0 1110-0011-X C Normal mode Yes Yes , Notes: X : Don t care A5~A0 : RAM addresses D3~D0 : RAM data D/C : Data/command mode Def. : Power on reset default All the bold forms, namely 1 1 0, 1 0 1, and 1 0 0, are mode commands. Of these, 1 0 0 indicates the command mode ID. If successive commands have been issued, the command mode ID except for the first command will be omitted. The source of the tone frequency and of the time base/WDT clock frequency can be derived from a 32.768kHz crystal oscillator. Calculation of the frequency is based on the system frequency sources as stated above. It is recommended that the host controller should initialize the HT1620 after power on reset, for power on reset may fail, which in turn leads to malfunctioning of the HT1620. 16 July 26, 1999 HT1620 Holtek Semiconductor Inc. (Headquarters) No.3 Creation Rd. II, Science-based Industrial Park, Hsinchu, Taiwan, R.O.C. Tel: 886-3-563-1999 Fax: 886-3-563-1189 Holtek Semiconductor Inc. (Taipei Office) 5F, No.576, Sec.7 Chung Hsiao E. Rd., Taipei, Taiwan, R.O.C. Tel: 886-2-2782-9635 Fax: 886-2-2782-9636 Fax: 886-2-2782-7128 (International sales hotline) Holtek Microelectronics Enterprises Ltd. RM.711, Tower 2, Cheung Sha Wan Plaza, 833 Cheung Sha Wan Rd., Kowloon, Hong Kong Tel: 852-2-745-8288 Fax: 852-2-742-8657 Copyright Ó 1999 by HOLTEK SEMICONDUCTOR INC. The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Holtek reserves the right to alter its products without prior notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.tw. 17 July 26, 1999