CC1010-RTY1 datasheet(47/152 Pages) TI

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CC1010

SWRS047

Page 47 of 152

16. 8051 Peripherals

CC1010 offers the following peripherals

units controlled by the 8051-compatible

core:

•

Four general-purpose I/O ports, with

26 I/O pins in total.

•

Two standard 8051 timers

•

Two timers with PWM functionality

•

Watchdog timer

•

Real-time clock

•

SPI master

•

Hardware DES encryption / decryption

•

Random bit generator

•

10-bit ADC

These modules are described in the

following sections.

16.1 General Purpose I/O

Four

general

purpose

I/O-ports

are

available: P0, P1, P2 and P3. Table 20

shows each port and the pins on each

port.

Each port is associated with two registers:

The port register (P0, P1, P2, or P3) and

the direction register (P0DIR, P1DIR,

P2DIR, or P3DIR).

Each bit in the Px registers has its

associated bit in the direction registers

PxDIR. Setting PxDIR.y will make Px.y

an input which can be read in Px(y). All

pins are inputs after reset. Clearing

PxDIR.y will make the pin Px.y output

the data from the register Px(y). All Px

and PxDIR register descriptions are

shown from page 49.

The structure for a single I/O-bit y on port

x is shown in Figure 7. Some ports have

alternate functions (such as the SPI

interface), which are enabled through

other registers (such as SPCR.SPE).

These alternate functions may or may not

override the direction setting from PxDIR

as shown.

When reading the Px registers, data is

read from the directly from the pin. When

using a read-modify-write instruction such

ANL Px, #0x01, the output register

value is read and modified regardless of

the setting in PxDIR.

Writing to the Px registers writes to the

output register, and sets the I/O pin state.

Using a read-modify-write operation reads

from the output register, modifies the value

according to the instruction executed and

writes the result back into the output

accordingly.

In practice, this means that the mov

instruction should only be used when

writing to all the pins in the port. To modify

only a few pins, use a read-modify-write

instruction. Also, be careful of using

constructs in C or another high-level

language that result in a mov from the Px

registers, modify the result and write it

back (without using read-modify-write

instructions), as this will cause problems if

not all I/O pins in the port are configured

as outputs. In C, the |=, &= and ^=

operators should be used to set, clear and

toggle pins respectively.

The

CC1010 ports deviate from the

standard 8051-port in the following ways:

•

No pull-ups / pull-downs on pins

•

Dedicated direction bits in PxDIR

registers

•

CMOS output levels on all ports

All general-purpose I/O pins are rated to

sink or source 2 mA, except pin P2.3,

which is rated to sink or source 8 mA.

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