Philips TPM754 Datasheet

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TPM754A

Microcontroller with TrackPoint microcode from IBM

Preliminary specification Replaces datasheet TPM754 of 1997 Dec 03 IC28 Data Handbook

1999 Nov 11

INTEGRATED CIRCUITS

Philips Semiconductors Preliminary specification

TPM754AMicrocontroller with TrackPoint microcode from IBM

1999 Nov 11

The Philips Semiconductors TPM754 is a small package, low cost, ROM-coded 80C51 with IBM’s TrackPoint pointing algorithms and control code. TrackPoint is the result of years of human factors research and innovation at IBM. The result is a “velocity sensitive” pointing solution more efficient and easier to use than “position sensitive” devices such as the mouse, the trackball, or the touchpad.

IBM has licensed Philips Semiconductors to sell microcontrollers with TrackPoint code. By purchasing a TPM from Philips, the purchaser becomes a sub-licensee of Philips. The selling price of Philips’ TPM includes the royalties for IBM’s intellectual property, which Philips in turn pays to IBM. Customers for TPMs do not need to sign any licensing agreement with either IBM or Philips. This code is the intellectual property of IBM, which is covered by numerous patents, and must be treated accordingly.

The TPM754 contains IBM TrackPoint code, a single module PCA, a 256 × 8 RAM, 21 I/O lines, two 16-bit counter/timers, a two-priority level interrupt structure, a full duplex serial channel, an on-chip oscillator, and an 8-bit D/A converter.

For identical device without TrackPoint code, see the 8XC754 datasheet.

FEA TURES

•80C51-based architecture

•Small package sizes – 28-pin SSOP

•Power control modes:

– Idle mode – Power-down mode

•256 × 8 RAM

•Two 16-bit auto reloadable counter/timers

•Single module PCA counter/timer

•Full duplex serial channel

•Boolean processor

•CMOS and TTL compatible

PIN CONFIGURATION

1 2 3 4 5 6 7 8

9 10 11 12 17

28RxD/T0/P3.4

TxD/T1/P3.5

ECI/P3.6

INT1

/P3.7

RST

X2 X1

ZIN YIN XIN

P3.3 P3.2 P3.1 P3.0 INT0

/P1.0 CEX/P1.1 V

XYDAC

P1.2

ZDAC/ASEL XYSOURCE XYDACBIASXYZRAMP

13 16 VREGAV

14 15 DECOUPLEAV

SU00726B

PLASTIC

SHRINK

SMALL

OUTLINE

PACKAGE

ORDERING INFORMA TION

ORDERING CODE

TEMPERATURE RANGE °C

AND PACKAGE

FREQUENCY

DRAWING

NUMBER

PTPM754A DB 0 to +70, 28-pin Shrink Small Outline Package 3.5 to 12 MHz SOT341-1

NOTE:

1. PTPM754A has improved start-up from low-voltage power down.

IBM is a registered trademark, and TrackPoint is a trademark of IBM Corporation.

Philips Semiconductors Preliminary specification

TPM754AMicrocontroller with TrackPoint microcode from IBM

1999 Nov 11

PIN DESCRIPTION

MNEMONIC DIP

PIN NO.

TYPE NAME AND FUNCTION

8 I Circuit Ground Potential.

22 I Supply voltage during normal, idle, and power-down operation.

P1.0–P1.2 21, 23, 24 I/O Port 1: Port 1 is a 3-bit bidirectional I/O port with internal pull-ups on P1.0 and P1.1. Port 1 pins that

have 1s written to them can be used as inputs. As inputs, port 1 pins that are externally pulled low will source current because of the internal pull-ups (P1.0, P1.1). (See DC Electrical Characteristics: I

). Port 1 also serves the special function features listed below (Note: P1.0 does not have the strong pullup that is on for 2 oscillator periods.):

24 I INT0 (P1.0): External interrupt 0. 23 O CEX (P1.1): PCA clock output.

P3.0–P3.7 1–4,

25–28

I/O Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s written to

them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 3 pins that are externally being pulled low will source current because of the pull-ups. (See DC Electrical Characteristics: I

). (Note: P3.5 does not have the strong pullup that is on for 2 oscillator periods.)

Port 3 also serves the special function as listed below:

3 I ECI (P3.6): External PCA clock input. 1 I RxD/T0 (P3.4): Serial port receiver data input.

Timer 0 external clock input. 4 I INT1: External interrupt 1. 2 I TxD/T1 (P3.5): Serial port transmitter data.

Timer 1 external clock input.

RST 5 I Reset: A high on this pin for two machine cycles while the oscillator is running resets the device.

(NOTE: The TPM754 does not have an internal reset resistor.)

X1 7 I Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock generator circuits. X2 6 O Crystal 2: Output from the inverting oscillator amplifier. AV

14 I Analog supply voltage and reference input.

13 I Analog supply and reference ground. ZIN 9 I ZIN: Input to analog multiplexer. YIN 10 I YIN: Input to analog multiplexer. XIN 11 I XIN: Input to analog multiplexer. XYZRAMP 12 O XYZRAMP: Provides a low impedance pulldown to VSS under S/W control. DECOUPLE 15 O DECOUPLE: Output from regulated supply for connection of decoupling capacitors. VREG 16 O VREG: Provides regulated analog supply output. XYDACBIAS 17 O XYDACBIAS: Provides source voltage for bias of external circuitry. XYSOURCE 18 O XYSOURCE: Provides source voltage from regulated analog supply. ZDAC 19 O ZDAC: Switchable output from the internal DAC. XYDAC 20 O XYDAC: Non-switchable output from the internal DAC.

NOTE:

1. AV

(reference ground) must be connected to 0 V (ground). AVCC (reference input) cannot differ from VCC by more than ±0.2 V , and must

be in the range 4.5 V to 5.5 V .

Philips Semiconductors Preliminary specification

TPM754AMicrocontroller with TrackPoint microcode from IBM

1999 Nov 11

OSCILLA T OR CHARACTERISTICS

X1 and X2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator.

To drive the device from an external clock source, X1 should be driven while X2 is left unconnected. There are no requirements on the duty cycle of the external clock signal, because the input to the internal clock circuitry is through a divide-by-two flip-flop. However, minimum and maximum high and low times specified in the data sheet must be observed.

IDLE MODE

The TPM754 includes the 80C51 power-down and idle mode features. In idle mode, the CPU puts itself to sleep while all of the on-chip peripherals except the D/A stays active. The functions that continue to run while in the idle mode are the timers and the interrupts. The instruction to invoke the idle mode is the last instruction executed in the normal operating mode before the idle mode is activated. The CPU contents, the on-chip RAM, and all of the special function registers remain intact during this mode. The idle mode can be terminated either by any enabled interrupt (at which time the process is picked up at the interrupt service routine and continued), or by a hardware reset which starts the processor in the same manner as a power-on reset. Upon powering-up the circuit, or exiting from idle mode, sufficient time must be allowed for stabilization of the internal analog reference voltages before a D/A conversion is started.

I/O Ports

The I/O pins provided by the TPM754 consist of port 1 and port 3.

Port 1

Port 1 is a 3-bit bidirectional I/O port and includes alternate functions on some pins of this port. Pins P1.0 and P1.1 are provided with internal pullups while the remaining pin (P1.2) has an open drain output structure. The alternate functions for port 1 are:

INT0

– External interrupt 0.

CEX – PCA clock output.

Port 3

Port 3 is an 8-bit bidirectional I/O port structure. The alternate functions for port 3 are: RxD – Serial port receiver data input.

T1 – Timer 1 external clock input. INT1

– External interrupt 1. TxD – Serial port transmitter data. T0 – Timer 0 external clock input. ECI – PCA external clock input.

Analog Section

The analog section of the TPM754, shown in Figure 1, consists of four major elements: a bandgap referenced voltage regulator, an 8-bit DAC, an input multiplexer and comparator, and a low impedance pulldown device.

The bandgap voltage regulator uses the AV

pin as its supply and produces a regulated output on the VREG pin. The regulator also supplies the analog supply voltage for the DAC. The regulator may be switched on/off by means of the AC1 bit in the analog control register (ACON0). The regulator output may also be supplied to the XYDACBIAS and XYSOURCE pins by means of bits AC3 and AC4, respectively. The DECOUPLE pin is provided for decoupling the regulator output.

The DAC is an 8-bit device and its output appears on the XYDAC pin. In addition, the DAC output may also be routed to the ZDAC pin by means of bit AC6 in the ACON0 register. The DAC output is not buffered, so external load impedances should be taken into consideration when using either of these outputs.

A 3-input multiplexer is provided, whose output is connected to the positive reference of a comparator. The multiplexer output is controlled by bits MUX2:0 of ACON1. A bandgap reference supplies the negative reference of the comparator. The output of the comparator may be used the trigger the capture input of module 4 of the PCA.

A low impedance pulldown is supplied at the XYZRAMP pin and is controlled by bit AC5 of ACON0.

The functions of the analog section are controlled by the IBM TrackPoint code embedded within the Philips TPM754.

PC BOARD LAYOUT CONSIDERATIONS

The TrackPoint is a low-level analog circuit. While not difficult to implement, careful consideration should be given to circuit board layout to obtain proper operation of the TrackPoint. The considerations are similar to that used for radio frequency application. The circuit should be located far from the CPU and video lines, and should also be shielded from any digital signals. A 100µV pulse picked up every 3 or 4 seconds is sufficient to cause cursor drift. A good circuit board layout will result in a circuit that is very stable and will hold the cursor on a pixel for days at a time. However, the autorouters of most software board layout packages will not do an adequate job, and manual routing of this portion of the motherboard is recommended.

The TPM754 has excellent supply regulation for the analog portions of the TrackPoint circuit. However , care should be taken with respect to the circuit ground to avoid voltage shifts due to non-TrackPoint loads. The analog part of the circuit must have its own ground plane, isolated from everything else and connected to the main ground at just one point (no ground loops). All of the analog portion of the TrackPoint circuit, and nothing else, must be over this ground island.

No digital traces can pass though the analog area on any level from the ground plane out. The circuit should be confined to one side of the ground plane, preferably on the first interior layer, with the ground plane next. The circuit should be powered only at a single point (pin 14), and that power should be filtered to ground before it comes onto the analog area.

The signal lines from the TrackPoint sensor stick can be sensitive to pickup, and should be run close together, and not too close to digital lines. A grounded guard trace is a good idea. Most important, the stick common line is not a ground line, but rather a signal line, although it will eventually connect to the analog ground. A common and serious error is to treat it as ground, connecting it to a general ground at some convenient point.

The layout should be designed to keep things compact and minimize trace lengths. The whole circuit, analog and digital, will fit comfortably within 2cm × 3cm. In some situations, it may be desirable to put the circuit on a separate card instead of on the motherboard. In this case, a shielded cable should provide the best means of connecting the stick signals to the circuit card.

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