Citizen CL-S400DT Technical Manual page 64

[While receiving PRIME signal]
PRIME
BUSY
Ack
Fault
SELECT
Note:
If the PRIME signal width is 10
BUSY goes to "High" when the PRIME signal is accepted by the printer.
[Timing relationship between BUSY and ACK]
BUSY
ACK
10~15µsec or more
sec or less, it is not accepted.
µ
2-51
Chapter 2 Operating Principles
Center
About 2 µsec
2-4. Interface
CL-S400DT