Suspend Resume - Fujitsu F2MC-16LX Hardware Manual

14.5.10

Suspend Resume

USB Mini-HOST supports suspend and resume operations.
Suspend Operation
When writing "1" to the SUSP bit of the host state status register (HSTATE),
• USB bus high impedance state
• Stop of circuit block where clock is not necessary
USB Mini-HOST follows the steps above, and puts the USB circuit in suspend status. When the USB
circuit is put in suspend status, it sets the SUSP bit of the host state status register (HSTATE) to "1".
It is inhibited for USB Mini-HOST to set the USB circuit to suspend status or stop clock supplied to the
circuit when the USB bus is being reset or the SOFBUSY of HSTATE is "1" or data is being sent or
received.
Resume Operation
Before it can start resume operation in suspend status, one of the following conditions must be true:
(1) Write "0" to the SUSP bit of the host state status register (HSTATE).
(2) The pins D+ and D- for Mini-Host are detected to be k-state.
(3) The device is detected being cut.
(4) The device is detected being connected.
After the RWKIRQ bit of the host interrupt register (HIRQ) is set to "1", an issuance of the token is
allowed. The followings show the operation timing for each condition.
Figure 14.5-11 Resume Operation by Register (Full Speed Mode)
(1) Write "0" to the SUSP bit of the host state status register (HSTATE)
Pin D+
for Mini-HOST
Pin D-
for Mini-HOST
RWKIRQ bit of HIRQ
(RWKIRE="1")
: Power output from USB Mini-HOST
: Drive by resistances of pull-up and pull-down
∗ : This value is not guaranteed.
To bit2 of HCNT
"0" Write
20µs ∗
CHAPTER 14 USB Mini-HOST
1.33µs ∗
1 bit time
349