MV20556 Datasheet, PDF (15/30 Pages) Mosel Vitelic, Corp – 8 - Bit MCU Mouse Controller

MOSEL VITELIC INC.
Preliminary
MV20556
Timer/Counter (Cont'd)
changes the timer's mode or alters its control bits, the
actual change occurs at the end of the instruction's
execution.
The T1 and T0 inputs are sampled near the falling-
edge of ALE in the tenth(10th), twenty-second(22nd),
thirty-fourth(34th) and forty-sixth(46th) oscillator periods
of the instruction-in-progress. They are also sampled
in the twenty-second oscillator period of MOVX despite
the absence of internal signal ALE. Thus, an external
reference's high and low times must each be a
minimum of twelve oscillator periods in duration. There
is a twelve oscillator period delay from when a toggled
input (transition from high to low) is sampled to when
the counter is ineremented.
Reading/Reloading
The timer/counters can be read and reloaded on the fly.
However, the 16-bit timer/counters must be read and
loaded as two 8-bit bytes. During a read the potential
"phasing error" can be programmed around, as follows:
RTC MOV A, TH0
MOV B, TL0
CJNE A, TH0, RTC
MSB
GATE
Timer 1
C/#T M1
Timer 0
M0 GATE C/#T M1
LSB
M0
GATE
C/#T
M1
M0
When TRx (in TCON) is set and GATE=1, TIMER/COUNTERx will run only while INTx pin is
high (hardware control). When GATE=0, TIMER/COUNTERx will run only while TRx=1
(software control).
Timer or counter selector. Cleared for timer operation (input from internal system clock).
Set for counter operation (input form Tx input pin).
Mode selector bit.
Mode selector bit.
M1
M0
Operating mode
0
0
Mode 0. (13-bit timer, by prescaled.)
0
1
Mode 1. (16-bit timer/counter)
1
0
Mode 2. (8-bit auto-load timer/counter)
1
1
Mode 3. (TL0 is an 8-bit timer/counter controlled by the standard timer 0
control bits. TH0 is an 8-bit timer and is controlled by timer 1 control bits.)
1
1
Mode 3. (Timer/counter 1 stopped).
TMOD definition
Specifications subject to change without notice, contact your sales representatives for the most recent information.
15/27
PID256** 07/97