Data Sheet For 8254 Programmable Interval Timer s/iW-8254... · Data Sheet for 8254 Programmable Interval Timer REL 1.0 iWave Systems Technologies Pvt. Ltd. Page 6 of 16 (Confidential)
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Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 1 of 16 (Confidential)
Data Sheet For 8254 Programmable Interval Timer
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 2 of 16 (Confidential)
DOCUMENT REVISION HISTORY
Revision Date Change Description Author
1.0 24th Dec ‘11 Initial Version KA REL 1.0 16th Aug ‘12 Removed implementation results VC PROPRIETARY NOTICE: This document contains proprietary material for the sole use of the intended recipient(s). Do not read this document further if you are not the intended recipient. Any review, use, distribution or disclosure by others is strictly prohibited. If you are not the intended recipient (or authorized to receive for the recipient), you are hereby notified that any disclosure, copy or distribution or use of any of the information contained within this document is STRICTLY PROHIBITED. Thank you. “iWave Systems Tech. Pvt. Ltd.”
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 3 of 16 (Confidential)
Table of Contents 1 INTRODUCTION________________________________________________________ 6
1.1 PURPOSE ____________________________________________________________ 6 1.2 FEATURES ___________________________________________________________ 6 1.3 ACRONYMS AND ABBREVIATIONS _________________________________________ 6
2 PROGRAMMABLE INTERVAL TIMER ___________________________________ 7
2.1 BLOCK DIAGRAM ______________________________________________________ 7 2.2 DESCRIPTION _________________________________________________________ 7 2.3 SIGNAL DESCRIPTION __________________________________________________ 9
3 TIMING WAVEFORMS _________________________________________________ 10
3.1 COUNT WRITE OPERATION (EX. MODE 0) __________________________________ 10 3.2 MODE 0 OPERATION __________________________________________________ 11 3.3 MODE 1 OPERATION __________________________________________________ 12 3.4 MODE 2 OPERATION __________________________________________________ 13 3.5 MODE 3 OPERATION __________________________________________________ 14 3.6 MODE 4 OPERATION __________________________________________________ 15 3.7 MODE 5 OPERATION __________________________________________________ 16
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 4 of 16 (Confidential)
List Of Figures Figure 1: Programmable Interval Timer Block Diagram ..............................................................7 Figure 2: Mode 0 Operation ...................................................................................................... 10 Figure 3:Mode 0 Operation ....................................................................................................... 11 Figure 4: Mode 1 Operation ...................................................................................................... 12 Figure 5: Mode 2 Operation ...................................................................................................... 13 Figure 6: Mode 3 Operation ...................................................................................................... 14 Figure 7: Mode 4 Operation ...................................................................................................... 15 Figure 8: Mode 5 Operation ...................................................................................................... 16
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 5 of 16 (Confidential)
List Of Tables Table 1: Acronyms & Abbreviations ...........................................................................................6 Table 2: Programmable Timer IO Signal description ..................................................................9
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 6 of 16 (Confidential)
1 Introduction 1.1 Purpose This document describes the Technical Specification 8254 programmable interval timer. It includes the overall features, detailed description, I/O specifications and resource utilization summary for the 8254 programmable interval timer.
1.2 Features Following are the 8254 Programmable interval timer features
Three independently operated 16-bit counters
Binary/BCD count operation
Multiple Latch command for easy monitoring
Counter Latch command
Six count modes available for each counter o Interrupt at the End of Count o GATE Re-triggerable One-Shot o Rate Generator o Square Wave Generator o Software-Triggered Strobe o Re-triggerable Hardware-Triggered Strobe
Functionally based on 8254
1.3 Acronyms and Abbreviations Table 1: Acronyms & Abbreviations
Term Meaning BCD Binary Coded Decimal
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
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2 Programmable Interval Timer 2.1 Block Diagram
Data Bus Buffer
Read/Write Control
ControlWord
Register
Counter-0
Counter-1
Counter-2
D_I[7:0]
IORD_N
IOWR_N
A[1:0]
CS_N
CLK0
OUT0
GATE0
CLK1
OUT1
GATE1
CLK2
OUT2
GATE2
control_word[7:0]
data_out[7:0]
read/write enable
data_in[7:0]
System InterfaceSystem Interface Counter InterfaceCounter Interface
D_O[7:0]
D_VAL_O
Figure 1: Programmable Interval Timer Block Diagram
2.2 Description The design implements 8254 Programmable Interval Timer/Counter used for timing control applications in microcomputer systems. Design is capable of generating accurate time delays under software control. Three independent 16-bit counters are supported which can be configured to operate in one of the six operating modes supported.
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 8 of 16 (Confidential)
Data Bus Buffer: This is a 8-bit, three-state buffer that interfaces the system bus to the remaining blocks of the design.
Read/Write Control: This block decodes the control and address inputs from the processor and generates control signals to the remaining blocks of the design.
Control Word Register: This is a 8-bit register into which the control words are written to determine the operation mode of the counter.
Counter #n (n=0, 1, 2): Three independent counters capable of binary or BCD operation are supported. Each counter supports six different modes configurable through software and can each be set to different operating modes.
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 9 of 16 (Confidential)
2.3 Signal Description Table 2: Programmable Timer IO Signal description
SIGNAL NAME I/O WIDTH DESCRIPTION
RESET I 1 Input reset signal D_I [7:0] I 8 8-bit input data bus D_O [7 :0] O 8 8 bit output data bus
D_VAL_O O 1 Output data valid signal A [1 :0] I 2 16-bit bidirectional data lines
CS_N I 1 Active low Chip select input IOWR_N I 1 Active low Write enable input
IORD_N I 1 Active low Read enable input CLK0 I 1 Determines the count rate for Counter-0
GATE0 I 1 This signal controls the operation of Counter-0 depending on the mode of operation
OUT0 O 1 Counter-0 output, operation depends on the count mode. Can be used as an interrupt source for the processor.
CLK1 I 1 Determines the count rate for Counter-1
GATE1 I 1 This signal controls the operation of Counter-1 depending on the mode of operation
OUT1 O 1 Counter-1 output, operation depends on the count mode. Can be used as an interrupt source for the processor.
CLK2 I 1 Determines the count rate for Counter-2
GATE2 I 1 This signal controls the operation of Counter-2 depending on the mode of operation
OUT2 O 1 Counter-2 output, operation depends on the count mode. Can be used as an interrupt source for the processor.
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 10 of 16 (Confidential)
3 Timing Waveforms 3.1 Count Write Operation (Ex. Mode 0)
CLK
IOWR_N LB =4H
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0000H FFFFH FFFEH FFFDH
IOWR_N CW =B0H
GATE
OUTCount Value 002FH 002EH 002EH 002EH 731CH
HB =73H
(Transfer)
(Transfer)
CLK
IOWR_N HB =44H
?
GATE
OUTCount Value ? ? 4400H 43FFH
(Transfer)
43FEH 43FDH 43FCH 43FBH 43FAH 43F9H 43F8H
CLK
0030H0031H0032H
LB =1CH
731BH 731AH 0001H 0000H
Figure 2: Mode 0 Operation
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 11 of 16 (Confidential)
3.2 Mode 0 Operation
CLK
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0000H FFFFH FFFEH FFFDH
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0003H 0002H
LB =3
0001H 0000H
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0000H FFFFH0003H 0003H
(Transfer)
(Transfer) (Transfer)
(Transfer)
Figure 3:Mode 0 Operation
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 12 of 16 (Confidential)
3.3 Mode 1 Operation
CLK
IOWR_N LB =2
?
GATE
OUTCount Value ? ? ? 0002H 0001H 0000H FFFFH
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0003H 0002H
LB =3
0001H 0000H
0002H 0001H 0000H FFFFH(Transfer) (Transfer)
(Transfer) (Transfer)
Figure 4: Mode 1 Operation
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 13 of 16 (Confidential)
3.4 Mode 2 Operation
CLK
IOWR_N LB =3
?
GATE
OUTCount Value ? ? 0003H 0002H 0001H
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0003H 0002H
LB =3
0001H 0003H
0003H 0002H 0001H 0003H 0002H 0001H
0002H
(Transfer) (Transfer) (Transfer)
(Transfer) (Transfer) (Transfer)
Figure 5: Mode 2 Operation
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
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3.5 Mode 3 Operation
CLK
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0002H 0004H 0002H
IOWR_N LB =5
?
GATE
OUTCount Value ? ? 0004H 0002H 0000H 0004H 0002H 0004H 0002H 0000H
0004H 0002H 0004H 0004H 0004H
(Transfer) (Transfer) (Transfer) (Transfer) (Transfer)
(Transfer) (Transfer) (Transfer) (Transfer)
Figure 6: Mode 3 Operation
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 15 of 16 (Confidential)
3.6 Mode 4 Operation
CLK
IOWR_N LB = 4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0000H FFFFH FFFEH FFFDH
IOWR_N LB = 4
?
GATE
OUTCount Value ? ? 0004H 0004H 0003H 0002H 0001H 0000H
IOWR_N LB = 5
?
GATE
OUTCount Value ? ? 0005H 0004H 0003H 0002H 0000H FFFFH0003H 0002H
FFFFH FFFEH
(Transfer)
(Transfer)
(Transfer)
LB = 3
0001H
(Transfer)
Figure 7: Mode 4 Operation
Data Sheet for 8254 Programmable Interval Timer
REL 1.0
iWave Systems Technologies Pvt. Ltd. Page 16 of 16 (Confidential)
3.7 Mode 5 Operation
CLK
IOWR_N LB =2
?
GATE
OUTCount Value ? ? ? 0002H 0001H 0000H FFFFH
IOWR_N LB =4
?
GATE
OUTCount Value ? ? 0004H 0003H 0002H 0001H 0000H FFFFH
LB =3
FFFEH 0003H
0002H 0001H 0002H 0001H
0002H
(Transfer) (Transfer) (Transfer)
(Transfer) (Transfer)
Figure 8: Mode 5 Operation
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