1996 Nov 25

9

Philips Semiconductors

Product specification

PCF84C00

6

FUNCTIONAL DESCRIPTION

6.1

‘Piggy-back’ version PCF84C00B

The PCF84C00B package has standard pinning on the

bottom to facilitate insertion as a mask-programmed

device. An EPROM can be mounted on top in an additional

socket. The total package height is greater than the height

of a standard DIP package. The PCF84C00B can address

up to 8 kbytes of external ROM/RAM, and has 256 bytes

of internal data RAM.

6.2

ROM-less version PCF84C00T

The PCF84C00T microcontroller contains no on-chip

ROM, but has all address and data lines brought out to

access an external ROM or EPROM. Consequently, this

version has more pins (see Fig.5) than the devices in the

PCF84CxxxA family with on-chip or ‘piggy-back’ ROM.

The PCF84C00T can address up to 8 kbytes of external

program memory, and has 256 bytes of internal data RAM.

6.3

Data memory

Data memory consists of 256 bytes of Random-Access

Memory (RAM). All locations are indirectly addressable

using RAM pointer registers; up to 16 designated locations

are directly addressable. Memory also includes an 8-level

program counter stack addressed by a 3-bit stack pointer.

6.4

I/O facilities

Each device has 23 I/O lines arranged as follows:

• Port 0; 8-bit parallel port (P0.0-P0.7)

• Port1; 8-bit parallel port (P1.0-P1.7)

• Port 2; 4-bit parallel port (P2.0-P2.3)

• INT/T0; External interrupt and test input. When used as

a test input, it can be directly tested by conditional

branch instructions JT0 and JNT0.

• T1; Test input which can alter program sequences when

tested by conditional jump instructions JT1 and JNT1.

T1 also functions as an input to the 8-bit timer/event

counter.

6.5

Reset

A positive-going signal on the RESET input/output:

• Sets the program counter to zero

• Selects location 0 of memory bank 0 and register bank 0

• Sets the stack pointer to zero (000); pointing to RAM

address 8

• Stops the timer/event counter, then sets it to zero

• Sets the timer prescaler to divide by 32

• Resets the timer flag

• Sets all ports except P2.3 to input mode

• Cancels Idle and Stop mode.

A negative-going signal on the RESET input/output:

• Sets P2.3/SDA and SCLK to HIGH after a maximum of

30 clock pulses

clock pulses

• Starts program execution after 1866 clock pulses.

7

LIMITING VALUES

Limiting values in accordance with the Absolute Maximum Rating System (IEC 134).

SYMBOL

PARAMETER

CONDITIONS

MIN.

MAX.

UNIT

supply voltage

−0.8

+8

V

all input voltages

−0.5

DC input current

−10

+10

mA

DC output current

−10

+10

mA

total power dissipation

−

125

mW

storage temperature

−65

+150

°C