T89C51CC01CA-7CTIM Atmel, T89C51CC01CA-7CTIM Datasheet - Page 6

• Manufacturer Part Number: T89C51CC01CA-7CTIM
• Description: IC 8051 MCU FLASH 32K 64BGA
• Manufacturer: Atmel
• Series: AT89C CANr

Specifications of T89C51CC01CA-7CTIM

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: CAN, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 34
• Program Memory Size: 32KB (32K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-BGA
• For Use With: AT89STK-06 - KIT DEMOBOARD 8051 MCU W/CAN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: T89C51CC01CA7CTIM

Quasi-Bidirectional Port
Operation
6
A/T89C51CC01
Table 1. Read-Modify-Write Instructions
It is not obvious the last three instructions in this list are Read-Modify-Write instructions.
These instructions read the port (all 8 bits), modify the specifically addressed bit and
write the new byte back to the latch. These Read-Modify-Write instructions are directed
to the latch rather than the pin in order to avoid possible misinterpretation of voltage
(and therefore, logic) levels at the pin. For example, a Port bit used to drive the base of
an external bipolar transistor can not rise above the transistor’s base-emitter junction
voltage (a value lower than VIL). With a logic one written to the bit, attempts by the CPU
to read the Port at the pin are misinterpreted as logic zero. A read of the latch rather
than the pins returns the correct logic-one value.
Port 1, Port 2, Port 3 and Port 4 have fixed internal pull-ups and are referred to as
"quasi-bidirectional" Ports. When configured as an input, the pin impedance appears as
logic one and sources current in response to an external logic zero condition. Port 0 is a
"true bidirectional" pin. The pins float when configured as input. Resets write logic one to
all Port latches. If logical zero is subsequently written to a Port latch, it can be returned
to input conditions by a logical one written to the latch.
Note:
Logical zero-to-one transitions in Port 1, Port 2, Port 3 and Port 4 use an additional pull-
up (p1) to aid this logic transition (see Figure 4.). This increases switch speed. This
extra pull-up sources 100 times normal internal circuit current during 2 oscillator clock
periods. The internal pull-ups are field-effect transistors rather than linear resistors. Pull-
ups consist of three p-channel FET (pFET) devices. A pFET is on when the gate senses
logical zero and off when the gate senses logical one. pFET #1 is turned on for two
oscillator periods immediately after a zero-to-one transition in the Port latch. A logical
one at the Port pin turns on pFET #3 (a weak pull-up) through the inverter. This inverter
and pFET pair form a latch to drive logical one. pFET #2 is a very weak pull-up switched
on whenever the associated nFET is switched off. This is traditional CMOS switch con-
vention. Current strengths are 1/10 that of pFET #3.
MOV Px.y, C
Instruction
CLR Px.y
SET Px.y
DJNZ
DEC
ANL
ORL
XRL
CPL
JBC
INC
Port latch values change near the end of Read-Modify-Write instruction cycles. Output
buffers (and therefore the pin state) update early in the instruction after Read-Modify-
Write instruction cycle.
Description
logical AND
logical OR
logical EX-OR
jump if bit = 1 and clear bit
complement bit
increment
decrement
decrement and jump if not zero
move carry bit to bit y of Port x
clear bit y of Port x
set bit y of Port x
Example
ANL P1, A
ORL P2, A
XRL P3, A
JBC P1.1, LABEL
CPL P3.0
INC P2
DEC P2
DJNZ P3, LABEL
MOV P1.5, C
CLR P2.4
SET P3.3
4129N–CAN–03/08