W79E217A Datasheet, PDF (50/207 Pages) Winbond – 8-bit Microcontroller

Preliminary W79E217A Data Sheet
BIT NAME
7-0 TA
FUNCTION
The Timed Access register controls the access to protected bits. To access
protected bits, the user must first write AAh to TA. This must be immediately
followed by a write of 55h to TA. Now a window is opened in the protected bits
for three machine cycles, during which the user can write to these bits. For detail
data, please refer "TIMED ACCESS PROTECTION" section.
TIMER 2 CONTROL
Bit:
7
6
5
4
3
2
1
0
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C / T2 CP /RL2
Mnemonic: T2CON
BIT NAME
7 TF2
6 EXF2
5 RCLK
4 TCLK
3 EXEN2
2 TR2
1 _C/T
0 _CP/RL2
Address: C8h
FUNCTION
Timer 2 overflows flag. This bit is set when Timer 2 overflows. It is also set when
the count is equal to the capture register in down count mode. It can be set only
if RCLK and TCLK are both 0. It is cleared only by software. Software can also
set this bit.
Timer 2 External Flag. A negative transition on the T2EX pin (P4.1) or timer 2
underflow/overflow will cause this flag to set based on ^{CP /RL2} , EXEN2 and
DCEN bits. If EXF2 is set by a negative transition, this flag must be cleared by
software. Setting this bit in software or detection of a negative transition on T2EX
pin will force a timer interrupt if enabled.
Receive clock Flag. This bit determines the serial port time-base when receiving
data in serial modes 1 or 3. If it is 0, then timer 1 overflow is used for baud rate
generation, else timer 2 overflow is used. Setting this bit forces timer 2 in baud
rate generator mode.
Transmit clock Flag: This bit determines the serial port time-base when
transmitting data in mode 1 and 3. If it is set to 0, the timer 1 overflow is used to
generate the baud rate clock; else timer 2 overflow is used. Setting this bit forces
timer 2 in baud rate generator mode.
Timer 2 External Enable. This bit enables the capture/reload function on the
T2EX pin if Timer 2 is not generating baud clocks for the serial port. If this bit is
0, then the T2EX pin will be ignored, else a negative transition detected on the
T2EX pin will result in capture or reload.
Timer 2 Run Control. This bit enables/disables the operation of timer 2. Halting
this will preserve the current count in TH2, TL2.
Counter/Timer select. This bit determines whether timer 2 will function as a timer
or a counter. Independent of this bit, the timer will run at 2 clocks per tick when
used in baud rate generator mode. If it is set to 0, then timer 2 operates as a
timer at a speed depending on T2M bit (CKCON.5), else, it will count negative
edges on T2 pin.
Capture/Reload Select. This bit determines whether the capture or reload
function will be used for timer 2. If either RCLK or TCLK is set, this bit will not
function and the timer will function in an auto-reload mode following each
overflow. If the bit is 0 then auto-reload will occur when timer 2 overflows or a
falling edge is detected on T2EX if EXEN2 =1. If this bit is 1, then timer 2
captures will occur when a falling edge is detected on T2EX if EXEN2=1.
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Publication Release Date: December 14, 2007
Revision A3.0