MK50H25 STMICROELECTRONICS [STMicroelectronics], MK50H25 Datasheet - Page 31

• Manufacturer Part Number: MK50H25
• Description: HIGH SPEED LINK LEVEL CONTROLLER
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

4.2.4 Timer/Counters
There are 5 independent counter-timers. The Host will write the value of these to the Initialization Block.
COUNTER
N1
N2
SCALER
T1
T3/T203
DESCRIPTION
MAXIMUM FRAME LENGTH. This field must contain the t wo’s complement of one
less than the maximum allowable frame length, in bytes. Any frame that exceeds this
count will be discarded.
MAXIMUM RETRANSMISSION COUNT. This field must contain the two’s complement
of one less than the maximum number of retransmissions that will be made following
the expiration of T1. If CSR2<14> bit EIBEN=1 then the MK50H25 will expect the value
for counter N2 to be located in the upper byte of IADR + 40.
TIMER PRESCALER. Timers T1, T3, and TP are scaled by this number. The prescaler is
incremented once every 32 system clock pulses. When it reaches the timers are incre-
mented and the prescaler is reset. This field is interpreted as two’s complement of the
prescaler period. If CSR2<14> bit EIBEN=1 then the MK50H25 will use the entire 16-bit
value at IADR+08 as the prescaler value. This may be required to achieve long timer
values when operating a high SYSCLK speeds. Note: a prescale value of 1 gives the
smallest amount of scalling to the timers (64 clock pulses); zero gives the largest (8224
clock pulses if EIBEN=0, or 2,097,184 clock pulses if EIBEN=1).
RETRANSMISSION TIMER. Link control frames will be retransmitted upon expiration of
the T1 timer if the appropriate response is not received. This field must contain the two’s
complement of the period of timer T1. The scaled value of T1 should be made large
enough to allow the remote station to receive the control frame and send its response.
LINK IDLE TIMER. The link idle timer determines the amount of link idle time necessary
to consider the link disconnected. If CSR2<12> bit T203E=1 it determines the amount of
link idle time or time without receiving a valid frame before it begins a RR/P=1 polling se-
quence to determine if the link is still connected. This field must contain the two’s com-
plement of the period of T3 or T203. T3 is disabled if CSR5<04> RTSEN = 1 or if the
MK50H25 is in Transparent mode.
IADR + 06
IADR + 08
IADR + 10
IADR + 12
IADR + 14
1
5
1
4
COUNTER N2
1
3
1
2
1
1
1
0
COUNTER N1
0
9
TIMER T1
TIMER T3
TIMER TP
0
8
0
7
0
6
0
5
SCALER
0
4
0
3
0
2
0
1
0
0
MK50H25
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