HMS91C8032 datasheet(35/157 Pages) HYNIX

35 / 157 page

HMS91C8032/97C8032

NOV., 2001 Ver 1.02

SERIAL PORT SET-UP

GENERATING BAUD RATES

Serial Port in Mode 0:

Timer/Counters need to be stop. Only the SCON register needs to be defined.

Serial Port in Mode 1:

Mode 1 has a variable baud rate. The baud rate can be generated by either Timer 1 or Timer 2

USING TIMER/COUNTER 1 TO GENERATE BAUD RATES:

For this purpose, Timer 1 is used in mode 2 (Auto-Reload). Refer to Timer Setup section of this chapter.

If SMOD = 0, then K =1.

If SMOD = 1, then K = 2. (SMOD is the PCON register).

Most of the timer the user knows the baud rate and needs to know the reload value for TH1.

Therefore, the equation to calculate TH1 can be written as:

TH1 must be an integer value. Rounding off TH1 to the nearest integer may not produce the desired baud rate. In this case, the user may

have to choose another crystal frequency.

Since the PCON register is not bit addressable, one way to set the bit is logical ORing the PCON register. (i.e., ORL PCON, #80H). The

address of PCON is 87H.

USING TIMER/COUNTER 2 TO GENERATE BAUD RATES:

For this purpose, Timer 2 must be used in the baud rate generating mode. If Timer 2 is being clocked through pin T2 the baud rate is:

MODE

SCON

SM2 VARIATION

10H

50H

90H

D0H

Single Processor

Environment

(SM2 = 0)

70H

B0H

F0H

Multiprocessor

Environment

(SM2 = 1)

Table 4-14 Serial Port

Baud Rate

CPU

---------------------

Baud Rate

CPU

256

TH1

()

–

[]

------------------------------------------------------------

TH1

256

CPU

384

Baud Rate

----------------------------------------

–

Baud Rate

Timer2 Overflow Rate

-------------------------------------------------------

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