82374EB Datasheet, PDF (78/208 Pages) Intel Corporation – SYSTEM COMPONENT (ESC)

82374EB 82374SB
3 3 4 TMSTAT TIMER STATUS BYTE FORMAT REGISTER
Register Location
Default Value
Attribute
Size
040h Timer 1 Counter 0
041h Timer 1 Counter 1
042h Timer 1 Counter 2
048h Timer 2 Counter 0
04Ah Timer 2 Counter 2
0xxxxxxxb
Read Only
8 Bits per counter
Each Counter’s Status Byte may be read following an Timer Read-Back Command The Read-Back command
is programmed through the counter control register If ‘‘Latch Status’’ is chosen as a Read-Back option for a
given counter the next read from the counter’s I O port address returns the Status byte
The Status byte returns the countdown type either BCD or binary the Counter Operational Mode the Read
Write Selection status the Null count also referred to as the Count Register Status and the current State of
the counter OUT pin
Bit
Description
7 Counter OUT Pin State When this bit is a 1 the OUT pin of the counter is also a 1 When this bit is a
0 the OUT pin of the counter is also a 0
6 Count Register Status Also referred to as Null Count indicates when the last count written to the
Count Register (CR) has been loaded into the counting element (CE) The exact time this happens
depends on the counter Mode and is described in the Mode definitions but until the count is loaded
into the counting element (CE) it can’t be read from the counter If the count is latched or read before
the load time the count value returned will not reflect the new count written to the register When bit 6
is a 0 the count has been transferred from CR to CE and is available for reading When bit 6 is a 1 the
Null count condition exists The count has not been transferred from CR to CE and is not yet available
for reading
5 4 Read Write Status Bits 5 4 reflect the read write selection made through bits 5 4 of the control
register The binary codes returned during the status read match the codes used to program the
counter read write selection
3 1 Mode Selection Status Bits 3 1 return the counter mode programming The binary code returned
matches the code used to program the counter mode as listed under the bit function above
0 Countdown Type Status Bit 0 reflects the current countdown type either 0 for binary countdown or a
1 for binary coded decimal (BCD) countdown
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