Siemens CPU 948 User Manual

Appendix 3: Technical Data of the CPU 948 and CPU 928B
Operation / Processing CPU 948 CPU 928B
Typical command execution times for bit commands:
with
F, I, Q
D
Formal operand
0.18
µs
0.7
µs
0.91
µs
0.57 µs
3.4
µs
2.4
µs
Typical command execution times for word commands:
- Load operations
L FY (byte)
L FW (word)
L FD (double word)
0.18 µs
0.5
µs
0.71
µs
0.81 µs
0.9
µs
1.6
µs
- Fixed point arithmetic
- Floating point arithmetic
0.55 ... 3.8
µs
3.3 ... 6.3
µs
0.9 ... 10.4
µs
9.1 ... 15.6
µs
Cyclic program execution (single processor mode)
Basic overhead calling OB 1/FB 0:
65/–
µs 104/106 µs
Extra time for process image updating depending on
the number of I/O bytes (n)
where 0 < n ≤128
n ≤ 64:
64
µs + n * 2.3 µs
n > 64:
92
µs + n * 2.3 µs
I: 14
µs + n * 1.1 µs
Q: 5
µs + n * 4.1 µs
Extra time for IPC flag transfer depending on the
number of IPC flags (n)
where 0 < n ≤ 256
n ≤ 64:
64
µs + n * 2.1 µs
n > 64:
92
µs + n * 2.1 µs
I: 14
µs + n * 1.4 µs
Q: 5
µs + n * 4.3 µs
Extra time for timer processing depending on the
timer block length
Timer block length (TBL) = 0
every 10 ms
11.6
µs
every 10 ms
10 µs
timer block length #0
n = number of timers running
(steps: 10 ms)
11.6
µs + TBL* 0.32 µs 16 µs + TBL * 0.2 µs
(no difference between
running and stopped
timers)
Interrupt driven program execution
Cycle time extension from nesting an empty OB 2
(without STEP 5 operations) at a block boundary
262
µs 300 µs
Reaction time
175
µs 270 µs
Appendix 3: Technical Data of the CPU 948 and CPU 928B
CPU 948 Programming Guide
C79000-G8576-C848-04
12 - 7

Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English