Philips PCD3350AH Datasheet

INTEGRATED CIRCUITS

DATA SHEET

PCD3350A

8-bit microcontroller with DTMF generator, 256 bytes EEPROM and real-time clock

Product specification

1996 Dec 18

Supersedes data of 1996 May 09

File under Integrated Circuits, IC03

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

CONTENTS

1FEATURES

2GENERAL DESCRIPTION

3ORDERING INFORMATION

4BLOCK DIAGRAM

5PINNING INFORMATION

5.1Pinning

5.2Pin description

6	FREQUENCY GENERATOR

6.1Frequency generator derivative registers

6.2Melody output (P1.7/MDY)

6.3DTMF clock divider and output (DP1.7/DCO)

6.4Frequency registers

6.5DTMF frequencies

6.6Modem frequencies

6.7Musical scale frequencies

7	EEPROM AND TIMER 2 ORGANIZATION

7.1EEPROM registers

7.2EEPROM latches

7.3EEPROM flags

7.4EEPROM macros

7.5EEPROM access

7.6Timer 2

8	REAL-TIME CLOCK

8.1Oscillator

8.2Divider chain

8.3Frequency adjustment

8.4Real-time clock derivative registers

9DERIVATIVE INTERRUPTS

10TIMING

11RESET

12IDLE MODE

13STOP MODE

14SUMMARY OF I/O PORTS AND ROM MASK OPTIONS

15SUMMARY OF DERIVATIVE REGISTERS

16HANDLING

17LIMITING VALUES

18DC CHARACTERISTICS

19AC CHARACTERISTICS

20PACKAGE OUTLINES

21SOLDERING

21.1Introduction

21.2Reflow soldering

21.3Wave soldering

21.4Repairing soldered joints

22DEFINITIONS

23LIFE SUPPORT APPLICATIONS

1996 Dec 18

2

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

1 FEATURES

∙8-bit CPU, ROM, RAM, EEPROM, real-time clock and I/O; all in a 44-lead quad flat package

∙8 kbytes ROM

∙256 bytes RAM

∙256 bytes Electrically Erasable Programmable Read Only Memory (EEPROM)

∙32 kHz crystal oscillator for Real-Time Clock (RTC)

∙EEPROM programmable RTC

∙Over 100 instructions (based on MAB8048) all of 1 or 2 cycles

∙34 quasi-bidirectional I/O port lines

∙8-bit programmable Timer/event counter 1

∙8-bit reloadable Timer 2

∙Three single-level vectored interrupts:

– external

– 8-bit programmable Timer/event counter 1

– derivative; triggered by reloadable Timer 2

∙Two test inputs, one of which also serves as the external interrupt input

∙DTMF, modem, musical tone generator

∙Reference for supply and temperature-independent tone output

∙Filtering for low output distortion (CEPT compatible)

∙Melody output for ringer application

∙Programmable DTMF clock divider

∙Power-on-reset

∙Stop and Idle modes

3 ORDERING INFORMATION (see note 1)

∙Supply voltage: 1.8 to 6 V (DTMF tone output and EEPROM erase/write from 2.5 V)

∙CPU clock frequency: 1 to 16 MHz (3.58 MHz or 10.74 MHz for DTMF)

∙Operating ambient temperature: −25 to +70 °C

∙Manufactured in silicon gate CMOS process.

2 GENERAL DESCRIPTION

This data sheet details the specific properties of the PCD3350A. The shared properties of the PCD33xxA family of microcontrollers are described in the “PCD33xxA family” data sheet, which should be read in conjunction with this publication.

The PCD3350A is a microcontroller designed primarily for telephony applications. It includes 8 kbytes ROM,

256 bytes RAM, 34 I/O lines, and an on-chip generator for dual tone multifrequency (DTMF), modem and musical tones. In addition to dialling, the generated frequencies can be made available as square waves for melody generation, providing ringer operation.

The PCD3350A also incorporates 256 bytes of EEPROM, permitting data storage without battery backup. The EEPROM can be used for storing telephone numbers, particularly for implementing redial functions.

Finally, the PCD3350A includes a low power 32 kHz crystal oscillator with an EEPROM programmable Real-Time Clock (RTC) working in standby mode.

The instruction set is similar to that of the MAB8048 and is a sub-set of that listed in the “PCD33xxA family” data sheet.

	TYPE NUMBER		PACKAGE
		NAME	DESCRIPTION	VERSION
	PCD3350AH	QFP44	plastic quad flat package; 44 leads (lead length 2.35 mm);	SOT205-1
			body 14 × 14 × 2.2 mm
	Note

1.Please refer to the Order Entry Form (OEF) for this device for the full type number to use when ordering. This type number will also specify the required program and the ROM mask options.

1996 Dec 18

3

18 Dec1996		BLOCK 4
		DIAGRAM

P2.0 to P2.3

TONE

DP1.0 to DP1.7/DCO

P1.0 to P1.7/MDY

P0.0 to P0.7

DP0.0/RCO to DP0.5

4

8

8

8

6

PORT 2

fDTMF

DER. PORT 1

PORT 1

RESIDENT

PORT 0

DER. PORT 0

PCD3350A

ROM

BUFFER

FILTER

BUFFER

BUFFER

8 kbytes

BUFFER

BUFFER

PORT 2

DER. PORT 1

PORT 1

PORT 0

DER. PORT 0

FLIP-FLOP

FLIP-FLOP

FLIP-FLOP

DECODE

FLIP-FLOP

FLIP-FLOP

INTERNAL

MEMORY

SINE WAVE

CLOCK

BANK

GENERATOR

FREQ.

FLIP-FLOPS

30

DTMF-CLOCK

32

TIMER/

HIGHER

LOWER

PROGRAM

HGF

LGF

& MELODY

EVENT

PROGRAM

PROGRAM

STATUS

CONTROL

REGISTER

REGISTER

T1

COUNTER

COUNTER

COUNTER

WORD

REGISTER

4

8

8

8

8

8

8

5

8

8

8

8

6

8

8

8

8

8

8

8

8

8

8

8

8

8

8

8

4

EEPROM

TIMER 2

TIMER 2

EEPROM

EEPROM

INTERRUPT

ACCUMULATOR

TEMPORARY

RAM

MULTIPLEXER

CLOCK

FREQUENCY

RELOAD

CONTROL

ADDRESS

DATA

CONTROL

ADJUSTMENT

REGISTER

LOGIC

REGISTER 1

REGISTER 0

REGISTER

REGISTER

REGISTER

TRANSFER

ADDRESS

REGISTER

REGISTER

REGISTER 1

REGISTER

timer interrupt

REGISTER 2

derivative

REGISTER 3

interrupt

ARITHMETIC

INSTRUCTION

REGISTER 4

REGISTER

REGISTER 5

REAL-TIME CLOCK

TEMPORARY

AND

D

REGISTER 6

DIVIDER CHAIN

DECODER

E

REGISTER 7

REGISTER 2

C

8 LEVEL STACK

O

EEPROM

(VARIABLE LENGTH)

LOGIC UNIT

D

256 bytes

E

OPTIONAL SECOND

T1

REGISTER BANK

REAL-TIME CLOCK

CE/T0

DECIMAL

CONDITIONAL

32 kHz OSCILLATOR

TIMER

POWER-ON-RESET

VPOR

external interrupt

ADJUST

DATA STORE

RTC1

RTC2

RTC interrupt

BRANCH

FLAG

LOGIC

CARRY

STOP

CONTROL AND TIMING

ACC

RESIDENT RAM ARRAY

RESET

IDLE

CE/T0

RESET

XTAL1

XTAL2

ACC BIT

256 bytes

TEST

INTERRUPT

INITIALIZE

OSCILLATOR

MED263

Fig.1 Block diagram.

256	bit-8
EEPROM bytes	microcontroller
clock time-real and	generator, DTMF with

PCD3350A

Semiconductors Philips

specification Product

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

5 PINNING INFORMATION

5.1Pinning

			P2.0		P1.7/MDY		P1.6		P1.5		P1.4		P1.3		V		TONE		V		P1.2		P1.1
															DD				SS
			44		43		42		41		40		39		38		37		36		35		34
P2.1	1																								33	P1.0
P2.2	2																								32	P0.7
P2.3	3																								31	P0.6
DP0.0/RCO	4																								30	P0.5
DP0.1	5																								29	P0.4
DP0.2	6									PCD3350AH															28	XTAL2
DP0.3																										XTAL1
	7																								27
DP0.4																										P0.3
	8																								26
DP0.5																										P0.2
	9																								25
RTC1	10																								24	P0.1
RTC2																										P0.0
	11																								23

	12			13		14		15		16		17		18		19		20		21		22
		CE/T0		T1		RESET		DP1.0		DP1.1		DP1.2		DP1.3		DP1.4		DP1.5		DP1.6		DP1.7/DCO

MED264

Fig.2 Pin configuration.

1996 Dec 18

5

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

5.2Pin description

Table 1 SOT205-1 package (for information on parallel I/O ports, see Chapter 14)

	SYMBOL		PIN		TYPE	DESCRIPTION
P2.1 to P2.3			1 to	3	I/O	3 bits of Port 2: 4-bit quasi-bidirectional I/O port
DP0.0/RCO			4		I/O	1 bit of Derivative Port 0: 6-bit quasi-bidirectional I/O port; or RTC output
DP0.1 to DP0.5			5 to	9	I/O	5 bits of Derivative Port 0: 6-bit quasi-bidirectional I/O port
RTC1			10		I	Real Time Clock 32 kHz oscillator input
RTC2			11		O	Real Time Clock 32 kHz oscillator output
			12		I	Chip Enable or Test 0 input
CE/T0
T1			13		I	Test 1/count input of 8-bit Timer/event counter 1
RESET			14		I	reset input
DP1.0 to DP1.6			15 to	21	I/O	7 bits of Derivative Port 1: 8-bit quasi-bidirectional I/O port
DP1.7/DCO			22		I/O	1 bit of Derivative Port 1: 8-bit quasi-bidirectional I/O port; or DTMF clock
						output
P0.0 to P0.3			23 to	26	I/O	4 bits of Port 0: 8-bit quasi-bidirectional I/O port
XTAL1			27		I	crystal oscillator/external clock input
XTAL2			28		O	crystal oscillator output
P0.4 to P0.7			29 to	32	I/O	4 bits of Port 0: 8-bit quasi-bidirectional I/O port
P1.0 to P1.2			33 to	35	I/O	3 bits of Port 1: 8-bit quasi-bidirectional I/O port
VSS			36		P	ground
TONE			37		O	DTMF output
VDD			38		P	positive supply voltage
P1.3 to P1.6			39 to	42	I/O	4 bits of Port 1: 8-bit quasi-bidirectional I/O port
P1.7/MDY			43		I/O	1 bit of Port 1: 8-bit quasi-bidirectional I/O port; or melody output
P2.0			44		I/O	1 bit of Port 2: 4-bit quasi-bidirectional I/O port

1996 Dec 18

6

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

6 FREQUENCY GENERATOR

A versatile frequency generator section with built-in programmable clock divider is provided (see Fig.3). The clock divider allows the DTMF section to run either

with the main clock frequency (fDTMF = fxtal) or with a third of it (fDTMF = 1¤3 ´ fxtal) depending on the state of the divider control bit DIV3 (see Table 4). The frequency generator

includes precision circuitry for dual tone multifrequency (DTMF) signals, which is typically used for tone dialling telephone sets.

6.1Frequency generator derivative registers

6.1.1HIGH AND LOW GROUP FREQUENCY REGISTERS

The TONE output can alternatively issue twelve modem frequencies for data rates between 300 and 1200 bits/s.

In addition to DTMF and modem frequencies, two octaves of musical scale in steps of semitones are available. Their frequencies are provided either in purely sinusoidal form on the TONE output or as a square wave on the port line P1.7/MDY. The latter is typically for ringer applications in telephone sets. If no frequency output is selected the TONE output is in 3-state mode.

Table 2 gives the addresses, symbols and access types of the High Group Frequency (HGF) and Low Group Frequency (LGF) registers, used to set the frequency output.

Table 2 Hexadecimal addresses, symbols, access types and bit symbols of the frequency registers

REGISTER	REGISTER	ACCESS				BIT SYMBOLS
ADDRESS	SYMBOL	TYPE	7	6	5	4	3	2	1	0
11H	HGF	W	H7	H6	H5	H4	H3	H2	H1	H0
12H	LGF	W	L7	L6	L5	L4	L3	L2	L1	L0

6.1.2CLOCK AND MELODY CONTROL REGISTER (MDYCON)

Table 3 Clock and Melody Control Register, MDYCON (address 13H; access type R/W)

7	6	5	4		3	2	1		0
0	0	0	0		0	EDCO	DIV3		EMO
Table 4 Description of MDYCON bits
BIT	SYMBOL				DESCRIPTION
7 to 3	-	These bits are set to a logic 0.
2	EDCO	Enable DTMF clock output. If bit EDCO = 0, then DP1.7/DCO is a general purpose
		derivative port line. If bit EDCO = 1, then DP1.7/DCO is the DTMF clock output.
		EDCO = 1 does not inhibit the port instructions for DP1.7/DCO. Therefore the state of
		both port line and flip-flop may be read in and the port flip-flop may be written by
		derivative port instructions. However, the port flip-flop of DP1.7/DCO must remain set to
		avoid conflicts between DTMF clock and port outputs.
1	DIV3	Enable DTMF clock divider. If bit DIV3 = 0, then the DTMF clock fDTMF = fxtal.
		If bit DIV3 = 1, then fDTMF = 1¤3 ´ fxtal.
0	EMO	Enable Melody Output. If bit EMO = 0, then P1.7/MDY is a standard port line.
		If bit EMO = 1, then P1.7/MDY is the melody output. EMO = 1 does not inhibit the port
		instructions for P1.7/MDY. Therefore the state of both port line and flip-flop may be read
		in and the port flip-flop may be written by port instructions. However, the port flip-flop of
		P1.7/MDY must remain set to avoid conflicts between melody and port outputs.
		When the HGF contents are zero while EMO = 1, P1.7/MDY is in the HIGH state.

1996 Dec 18

7

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

handbook, full pagewidth		fxtal
	8	CLOCK AND MELODY
		CONTROL REGISTER
	8	HGF REGISTER
8	INTERNAL BUS
	8	LGF REGISTER

	CLOCK	fDTMF				PORT/CLOCK
	DIVIDER
						OUTPUT LOGIC

PORT/MELODY

OUTPUT LOGIC

square wave

DIGITAL

SINE WAVE

SYNTHESIZER

DAC

SWITCHED

SWITCHED

CAPACITOR

CAPACITOR

RC LOW-PASS

BANDGAP

LOW-PASS

FILTER

VOLTAGE

FILTER

REFERENCE

MGB782

DAC

DIGITAL

SINE WAVE

SYNTHESIZER

Fig.3 Block diagram of the frequency generator, melody output (P1.7/MDY) and DTMF clock output (DP1.7/DCO).

DP1.7/

DCO

P1.7/

MDY

TONE

6.2Melody output (P1.7/MDY)

The melody output (P1.7/MDY) is very useful for generating musical notes when a purely sinusoidal signal is not required, such as for ringer applications.

The square wave (duty cycle = 12¤23 or 52%) will include the attenuated harmonics of the base frequency, which is defined by the contents of the HGF register (Table 2). However, even higher frequency notes may be produced since the low-pass filtering on the TONE output is not applied to the P1.7/MDY output. This results in the minimum decimal value x in the HGF register (see equation in Section 6.4) being 2 for the P1.7/MDY output, rather than 60 for the TONE output. A sinusoidal TONE output is produced at the same time as the melody square wave, but due to the filtering, the higher frequency sine waves produced when x < 60 will not appear at the TONE output.

Since the melody output is shared with P1.7, the port flip-flop of P1.7 has to be set HIGH before using the melody output. This is to avoid conflicts between melody and port outputs. The melody output drive depends on the configuration of port P1.7/MDY, see Chapter 14, Table 27.

6.3DTMF clock divider and output (DP1.7/DCO)

The DTMF clock divider allows the DTMF part to run either

with the main clock frequency (fDTMF = fxtal) or with a third of it (fDTMF = 1¤3 ´ fxtal) depending on the state of the divider control bit DIV3 in register MDYCON.

For low power applications, a 3.58 MHz quartz crystal or PXE resonator can be chosen together with the divide-by-one function of the clock divider.

For other applications a 10.74 MHz quartz crystal or PXE resonator may be chosen together with the divide-by-three function of the clock divider. This triples the program speed of the microcontroller, thereby keeping the assumed DTMF frequency of 3.58 MHz.

Since a 3.58 MHz clock is needed for peripheral telephony circuits such as the analog voice scrambler/descrambler PCD4440T, a switchable DTMF clock output is provided depending on the state of the enable clock output bit EDCO in register MDYCON.

1996 Dec 18

8

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

If EDCO = 1 and DIV3 = 1 in the MDYCON register: a

square wave with the frequency fDTMF = 1¤3 ´ fxtal is output on the derivative port line DP1.7/DCO. If EDCO = 1 and

DIV3 = 0: a square wave with the frequency fDTMF = fxtal is output on the derivative port line DP1.7/DCO.

The melody output drive depends on the configuration of port P1.7/MDY, see Chapter 14, Table 27.

6.4Frequency registers

The two frequency registers HGF and LGF define two frequencies. From these, the digital sine synthesizers together with the Digital-to-Analog Converters (DACs) construct two sine waves. Their amplitudes are precisely scaled according to the bandgap voltage reference. This ensures tone output levels independent of supply voltage and temperature. The amplitude of the Low Group Frequency sine wave is attenuated by 2 dB compared to the amplitude of the High Group Frequency sine wave.

The two sine waves are summed and then filtered by an on-chip switched capacitor and RC low-pass filters. These guarantee that all DTMF tones generated fulfil the CEPT recommendations with respect to amplitude, frequency deviation, total harmonic distortion and suppression of unwanted frequency components.

The value 00H in a frequency register stops the corresponding digital sine synthesizer. If both frequency registers contain 00H, the whole frequency generator is shut off, resulting in lower power consumption.

The frequency ‘f’ of the sine wave generated from either of the frequency registers is a function of the clock frequency

‘fxtal’ and the decimal value ‘x’ held in the register. The equation relating these variables is:

fxtal		£ x £ 255.
f = --------------------------------[23 (x + 2) ]	; where 60

The frequency limitation given by x ³ 60 is due to the low-pass filters which would attenuate higher frequency sine waves.

6.5DTMF frequencies

Assuming an oscillator frequency fxtal = 3.58 MHz, the DTMF standard frequencies can be implemented as

shown in Table 5.

The relationships between telephone keyboard symbols, DTMF frequency pairs and the frequency register contents are given in Table 6.

Table 5 DTMF standard frequencies and their implementation; value = LGF, HGF contents

VALUE	FREQUENCY (Hz)		DEVIATION
(HEX)	STANDARD	GENERATED	(%)	(Hz)
DD	697	697.90	0.13	0.90
C8	770	770.46	0.06	0.46
B5	852	850.45	-0.18	-1.55
A3	941	943.23	0.24	2.23
7F	1209	1206.45	-0.21	-2.55
72	1336	1341.66	0.42	5.66
67	1477	1482.21	0.35	5.21
5D	1633	1638.24	0.32	5.24

Table 6 Dialling symbols, corresponding DTMF frequency pairs and frequency register contents

TELEPHONE	DTMF FREQ.	LGF	HGF
KEYBOARD	PAIRS	VALUE	VALUE
SYMBOLS	(Hz)	(HEX)	(HEX)
0	(941, 1336)	A3	72
1	(697, 1209)	DD	7F
2	(697, 1336)	DD	72
3	(697, 1477)	DD	67
4	(770, 1209)	C8	7F
5	(770, 1336)	C8	72
6	(770, 1477)	C8	67
7	(852, 1209)	B5	7F
8	(852, 1336)	B5	72
9	(852, 1477)	B5	67
A	(697, 1633)	DD	5D
B	(770, 1633)	C8	5D
C	(852, 1633)	B5	5D
D	(941, 1633)	A3	5D
·	(941, 1209)	A3	7F
#	(941, 1477)	A3	67

1996 Dec 18

9

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

6.6Modem frequencies

Again assuming an oscillator frequency fxtal = 3.58 MHz, the standard modem frequencies can be implemented as in Table 7. It is suggested to define the frequency by the HGF register while the LGF register contains 00H, disabling Low Group Frequency generation.

Table 7 Standard modem frequencies and their implementation

	HGF	FREQUENCY (Hz)		DEVIATION
	VALUE
		MODEM	GENERATED	(%)	(Hz)
	(HEX)
	9D	980(1)	978.82	−0.12	−1.18
	82	1180(1)	1179.03	−0.08	−0.97
	8F	1070(2)	1073.33	0.31	3.33
	79	1270(2)	1265.30	−0.37	−4.70
	80	1200(3)	1197.17	−0.24	−2.83
	45	2200(3)	2192.01	−0.36	−7.99
	76	1300(4)	1296.94	−0.24	−3.06
	48	2100(4)	2103.14	0.15	3.14
	5C	1650(1)	1655.66	0.34	5.66
	52	1850(1)	1852.77	0.15	2.77
	4B	2025(2)	2021.20	−0.19	−3.80
	44	2225(2)	2223.32	−0.08	−1.68

Notes

1.Standard is V.21.

2.Standard is Bell 103.

3.Standard is Bell 202.

4.Standard is V.23.

6.7Musical scale frequencies

Finally, two octaves of musical scale in steps of semitones can be realized, again assuming an oscillator frequency

fxtal = 3.58 MHz (Table 8). It is suggested to define the frequency by the HGF register while the LGF contains

00H, disabling Low Group Frequency generation.

Table 8 Musical scale frequencies and their implementation

		HGF	FREQUENCY (Hz)
	NOTE	VALUE
			STANDARD(1)	GENERATED
		(HEX)
	D#5	F8	622.3	622.5
	E5	EA	659.3	659.5
	F5	DD	698.5	697.9
	F#5	D0	740.0	741.1
	G5	C5	784.0	782.1
	G#5	B9	830.6	832.3
	A5	AF	880.0	879.3
	A#5	A5	923.3	931.9
	B5	9C	987.8	985.0
	C6	93	1046.5	1044.5
	C#6	8A	1108.7	1111.7
	D6	82	1174.7	1179.0
	D#6	7B	1244.5	1245.1
	E6	74	1318.5	1318.9
	F6	6D	1396.9	1402.1
	F#6	67	1480.0	1482.2
	G6	61	1568.0	1572.0
	G#6	5C	1661.2	1655.7
	A6	56	1760.0	1768.5
	A#6	51	1864.7	1875.1
	B6	4D	1975.5	1970.0
	C7	48	2093.0	2103.3
	C#7	44	2217.5	2223.3
	D7	40	2349.3	2358.1
	D#7	3D	2489.0	2470.4

Note

1. Standard scale based on A4 @ 440 Hz.

1996 Dec 18

10

Philips Semiconductors	Product specification

8-bit microcontroller with DTMF generator,

PCD3350A

256 bytes EEPROM and real-time clock

7 EEPROM AND TIMER 2 ORGANIZATION

The PCD3350A has 256 bytes of Electrically Erasable Programmable Read Only Memory (EEPROM). Such non-volatile storage provides data retention without the need for battery backup. In telecom applications, the EEPROM is used for storing redial numbers and for short dialling of frequently used numbers. More generally, EEPROM may be used for customizing microcontrollers, such as to include a PIN code or a country code, to define trimming parameters, to select application features from the range stored in ROM.

The most significant difference between a RAM and an EEPROM is that a bit in EEPROM, once written to a logic 1, cannot be cleared by a subsequent write operation. Successive write accesses actually perform a logical OR with the previously stored information. Therefore, to clear a bit, the whole byte must be erased and re-written with the particular bit cleared. Thus, an erase-and-write operation is the EEPROM equivalent of a RAM write operation.

Whereas read access times to an EEPROM are comparable to RAM access times, write and erase access times are much slower at 5 ms each. To make these operations more efficient, several provisions are available in the PCD3350A.

First, the EEPROM array is structured into 64 four-byte pages (see Fig.4) permitting access to 4 bytes in parallel (write page, erase/write page and erase page). It is also possible to erase and write individual bytes.

Finally, the EEPROM address register provides auto-incrementing, allowing very efficient read and write accesses to sequential bytes.

To simplify the erase and write timing, the derivative 8-bit down-counter (Timer 2) with reload register is provided. In addition to EEPROM timing, Timer 2 can be used for general real-time tasks, such as for measuring signal duration and for defining pulse widths.

1996 Dec 18

11