DESCRIPTION

The PTN3501 is a general purpose maintenance and control device. It features an on-board E2PROM that can be used to store error codes or board manufacturing data for read??back by application software for diagnostic purposes.

The eight quasi bidirectional data pins can be independently assigned as inputs or outputs to monitor board level status or activate indicator devices such as LEDs.

The PTN3501 has six address pins allowing up to 64 devices to share the common two wire I2C software protocol serial data bus.

The PTN3501 supports live insertion to facilitate usage in removable cards on backplane systems.

The PTN3501 is an alternative to the functionally similar PTN3500 for systems where a high number of devices are required to share the same I2C-bus without need for an additional I2C-bus I/O expander.

PIN DESCRIPTION

CHARACTERISTICS OF THE I2C-BUS

The I2C-bus is for 2-way, 2-line communication between different ICs or modules. The two lines are a serial data line (SDA) and a serial clock line (SCL). Both lines must be connected to a positive supply via a pull-up resistor when connected to the output stages of a device. Data transfer may be initiated only when the bus is not busy.

Bit transfer

Start and stop conditions

Both data and clock lines remain HIGH when the bus is not busy. A HIGH-to-LOW transition of the data line, while the clock is HIGH is defined as the start condition (S). A LOW-to-HIGH transition of the data line while the clock is HIGH is defined as the stop condition (P) (see Figure 4).

One data bit is transferred during each clock phase. The data on the

SDA line must remain stable during the HIGH period of the clock pulse as changes in the data line at this time will be interpreted as control signals (See Figure 3).

System configuration

A device generating a message is a ??transmitter??, a device receiving is the ??receiver??. The device that controls the message is the ??master?? and the devices which are controlled by the master are the

??slaves?? (see Figure 5).

Acknowledge (see Figure 6)

The number of data bytes transferred between the start and the stop conditions from transmitter to receiver is not limited. Each byte of eight bits is followed by one acknowledge bit. The acknowledge bit is a HIGH level put on the bus by the transmitter whereas the master generates an extra acknowledge related clock pulse.

A slave receiver which is addressed must generate an acknowledge after the reception of each byte. Also a master must generate an acknowledge after the reception of each byte that has been clocked

out of the slave transmitter. The device that acknowledges has to pull down the SDA line during the acknowledge clock pulse, so that the SDA line is stable LOW during the HIGH period of the acknowledge related clock pulse, set??up and hold times must be taken into account.

A master receiver must signal an end of data to the transmitter by not generating an acknowledge on the last byte that has been clocked out of the slave. In this event the transmitter must leave the data line HIGH to enable the master to generate a stop condition.

WRITE PULSE

DATA FROM

SHIFT REGISTER

POWER-ON

RESET

READ PULSE

DATA TO

SHIFT REGISTER

100 ??A

D Q

FF

CI

S

VDD

P0 TO P7

VSS

TO INTERRUPT LOGIC

SW00788

Interrupt (see Figs 11 and 12)

The PTN3501 provides an open drain output (INT) which can be fed to a corresponding input of the microcontroller. This gives these chips a type of master function which can initiate an action elsewhere in the system.

An interrupt is generated by any rising or falling edge of the port inputs in the input mode. After time tiv the signal INT is valid.

Resetting and reactivating the interrupt circuit is achieved when data on the port is changed to the original setting or data is read from or written to the port which has generated the interrupt.

Resetting occurs as follows:

???In the READ mode at the acknowledge bit after the rising edge of the SCL signal

???In the WRITE mode at the acknowledge bit after the

HIGH??to??LOW transition of the SCL signal

???Returning of the port data to its original setting. A second port state change will require an SCL rising clock edge to be captured as an INT event.

???Interrupts which occur during the acknowledge clock pulse may be lost (or very short) due to the resetting of the interrupt during this pulse.

Each change of the I/Os after resetting will be detected and, after the next rising clock edge, will be transmitted as INT. Reading from or writing to another device does not affect the interrupt circuit.

MEMORY OPERATIONS

Write operations

Write operations require an additional address field to indicate the memory address location to be written. The address field is eight bits long providing access to any one of the 256 words of memory. There are two types of write operations, byte write and page write.

Byte Write (see Figure 14)

To perform a byte write the start condition is followed by the memory slave address and the R/W bit set to 0. The PTN3501 will respond with an acknowledge and then consider the next eight bits sent as the word address and the eight bits after the word address as the data. The PTN3501 will issue an acknowledge after the receipt of both the word address and the data. To terminate the data transfer

the master issues the stop condition, initiating the internal write cycle to the non??volatile memory. Only write and read operations to the quasi??bidirectional I/Os are allowed during the internal write cycle.

Page Write (see Figure 15)

A page write is initiated in the same way as the byte write, if after sending the first word of data, the stop condition is not received the PTN3501 considers subsequent words as data. After each data word the PTN3501 responds with an acknowledge and the four least significant bits of the memory address field are incremented. Should the master not send a stop condition after 16 data words the address counter will return to its initial value and overwrite the data previously written. After the receipt of the stop condition the inputs will behave as with the byte write during the internal write cycle.

Read operations

PTN3501 read operations are initiated in an identical manner to write operations with the exception that the memory slave address' R/W bit is set to a one. There are three types of read operations; current address, random and sequential.

Current Address Read (see Figure 16)

The PTN3501 contains an internal address counter that increments after each read or write access, as a result if the last word accessed was at address n then the address counter contains the address n+1.

When the PTN3501 receives its memory slave address with the

R/W bit set to one it issues an acknowledge and uses the next eight clocks to transmit the data contained at the address stored in the address counter. The master ceases the transmission by issuing the stop condition after the eighth bit. There is no ninth clock cycle for the acknowledge.

Random Read (see Figure 17)

The PTN3501's random read mode allows the address to be read from to be specified by the master. This is done by performing a dummy write to set the address counter to the location to be read.

The master must perform a byte write to the address location to be read, but instead of transmitting the data after receiving the acknowledge from the PTN3501 the master reissues the start condition and memory slave address with the R/W bit set to one. The PTN3501 will then transmit an acknowledge and use the next eight clock cycles to transmit the data contained in the addressed location. The master ceases the transmission by issuing the stop condition after the eighth bit, omitting the ninth clock cycle acknowledge.

Sequential Read (see Figure 18)

The PTN3501 sequential read is an extension of either the current address read or random read. If the master doesn't issue a stop condition after it has received the eighth data bit, but instead issues an acknowledge, the PTN3501 will increment the address counter and use the next eight cycles to transmit the data from that location. The master can continue this process to read the contents of the entire memory. Upon reaching address 255 the counter will return to address 0 and continue transmitting data until a stop condition is received. The master ceases the transmission by issuing the stop condition after the eighth bit, omitting the ninth clock cycle acknowledge.

SOLDERING

Introduction

There is no soldering method that is ideal for all IC packages. Wave soldering is often preferred when through-hole and surface mounted components are mixed on one printed-circuit board. However, wave soldering is not always suitable for surface mounted ICs, or for printed-circuits with high population densities. In these situations reflow soldering is often used.

This text gives a very brief insight to a complex technology. A more in-depth account of soldering ICs can be found in our IC Package Databook (order code 9398 652 90011).

DIP

Soldering by dipping or by wave

The maximum permissible temperature of the solder is 260??C; solder at this temperature must not be in contact with the joint for more than 5 seconds. The total contact time of successive solder waves must not exceed 5 seconds.

The device may be mounted up to the seating plane, but the temperature of the plastic body must not exceed the specified maximum storage temperature (Tstg max). If the printed-circuit board has been pre-heated, forced cooling may be necessary immediately after soldering to keep the temperature within the permissible limit.

Repairing soldered joints

Apply a low voltage soldering iron (less than 24 V) to the lead(s) of the package, below the seating plane or not more than 2 mm above it. If the temperature of the soldering iron bit is less than 300??C it may remain in contact for up to 10 seconds. If the bit temperature is between 300 and 400??C, contact may be up to 5 seconds.

SO and SSOP

Reflow soldering

Reflow soldering techniques are suitable for all SO and SSOP packages.

Reflow soldering requires solder paste (a suspension of fine solder particles, flux and binding agent) to be applied to the printed-circuit board by screen printing, stencilling or pressure-syringe dispensing before package placement.

Several techniques exist for reflowing; for example, thermal conduction by heated belt. Dwell times vary between 50 and 300

seconds depending on heating method. Typical reflow temperatures range from 215 to 250??C.

Preheating is necessary to dry the paste and evaporate the binding agent. Preheating duration: 45 minutes at 45??C.

Wave soldering

Wave soldering is not recommended for SSOP packages. This is because of the likelihood of solder bridging due to closely-spaced leads and the possibility of incomplete solder penetration in multi-lead devices.

If wave soldering cannot be avoided, the following conditions must be observed:

???A double-wave (a turbulent wave with high upward pressure followed by a smooth laminar wave) soldering technique should be used.

???The longitudinal axis of the package footprint must be parallel to the solder flow and must incorporate solder thieves at the downstream end.

Even with these conditions, only consider wave soldering SSOP packages that have a body width of 4.4 mm, that is SSOP16 (SOT369??1) or SSOP20 (SOT266??1).

During placement and before soldering, the package must be fixed with a droplet of adhesive. The adhesive can be applied by screen printing, pin transfer or syringe dispensing. The package can be soldered after the adhesive is cured.

Maximum permissible solder temperature is 260??C, and maximum duration of package immersion in solder is 10 seconds, if cooled to less than 150??C within 6 seconds. Typical dwell time is 4 seconds at 250??C.

A mildly-activated flux will eliminate the need for removal of corrosive residues in most applications.

Repairing soldered joints

Fix the component by first soldering two diagonally opposite end leads. Use only a low voltage soldering iron (less than 24 V) applied to the flat part of the lead. Contact time must be limited to

10 seconds at up to 300 ??C. When using a dedicated tool, all other leads can be soldered in one operation within 2 to 5 seconds between 270 and 320??C.

Philips Semiconductors

811 East Arques Avenue

P.O. Box 3409

Sunnyvale, California 94088??3409

Telephone 800-234-7381

??? Copyright Philips Electronics North America Corporation 2001 All rights reserved. Printed in U.S.A.

Date of release: 01-01