Intel 386 - Manual (Page 629)

Intel386™ EX EMBEDDED MICROPROCESSOR USER’S MANUAL
D-64
D.66 TMRCON
Timer Control (Control Word Format)
TMRCON Expanded Addr:
ISA Addr:
Reset State: F043H
0043H
XXH
7 0
SC1 SC0 RW1 RW0 M2 M1 M0 CNTFMT
Bit
Number
Bit
Mnemonic
Function
7–6 SC1:0 Select Counter:
Use these bits to specify a particular counter. The selections you make for
bits 5–0 define this counter’s operation.
00 = counter 0
01 = counter 1
10 = counter 2
11 is not an option for TMRCON’s control word format. Selecting 11
accesses TMRCON’s read-back format, which is shown in Figure 10-29.
5–4 RW1:0 Read/Write Select:
These bits select a read/write option for the counter specified by bits 7–6.
01 = read/write least-significant byte only
10 = read/write most-significant byte only
11 = read/write least-significant byte first, then most-significant byte
00 is not an option for TMRCON’s control word format. Selecting 00
accesses TMRCON’s counter-latch format, which is shown in Figure
10-27.
3–1 M2:0 Mode Select:
These bits select an operating mode for the counter specified by bits 7–6.
000 = mode 0
001 = mode 1
X10 = mode 2
X11 = mode 3
100 = mode 4
101 = mode 5
X is a don’t care.
0 CNTFMT Count Format:
This bit selects the count format for the counter specified by bits 7–6.
0 = binary (16 bits)
1 = binary coded decimal (4 decades)